diff --git a/extensions/git/src/repository.ts b/extensions/git/src/repository.ts
index 377851c5bcd..d37dc945f55 100644
--- a/extensions/git/src/repository.ts
+++ b/extensions/git/src/repository.ts
@@ -1476,9 +1476,9 @@ export class Repository implements Disposable {
 		const [refs, remotes, submodules, rebaseCommit] = await Promise.all([this.repository.getRefs({ sort }), this.repository.getRemotes(), this.repository.getSubmodules(), this.getRebaseCommit()]);
 
 		this._HEAD = HEAD;
-		this._refs = refs;
-		this._remotes = remotes;
-		this._submodules = submodules;
+		this._refs = refs!;
+		this._remotes = remotes!;
+		this._submodules = submodules!;
 		this.rebaseCommit = rebaseCommit;
 
 		const index: Resource[] = [];
diff --git a/src/vs/base/browser/ui/button/button.ts b/src/vs/base/browser/ui/button/button.ts
index 575122ccd77..de4d35ef320 100644
--- a/src/vs/base/browser/ui/button/button.ts
+++ b/src/vs/base/browser/ui/button/button.ts
@@ -128,15 +128,15 @@ export class Button extends Disposable {
 
 	private applyStyles(): void {
 		if (this._element) {
-			const background = this.buttonBackground ? this.buttonBackground.toString() : null;
+			const background = this.buttonBackground ? this.buttonBackground.toString() : '';
 			const foreground = this.buttonForeground ? this.buttonForeground.toString() : null;
-			const border = this.buttonBorder ? this.buttonBorder.toString() : null;
+			const border = this.buttonBorder ? this.buttonBorder.toString() : '';
 
 			this._element.style.color = foreground;
 			this._element.style.backgroundColor = background;
 
-			this._element.style.borderWidth = border ? '1px' : null;
-			this._element.style.borderStyle = border ? 'solid' : null;
+			this._element.style.borderWidth = border ? '1px' : '';
+			this._element.style.borderStyle = border ? 'solid' : '';
 			this._element.style.borderColor = border;
 		}
 	}
diff --git a/src/vs/base/browser/ui/iconLabel/iconLabel.ts b/src/vs/base/browser/ui/iconLabel/iconLabel.ts
index b9fc4154234..0122e851bab 100644
--- a/src/vs/base/browser/ui/iconLabel/iconLabel.ts
+++ b/src/vs/base/browser/ui/iconLabel/iconLabel.ts
@@ -77,7 +77,7 @@ class FastLabelNode {
 		}
 
 		this._empty = empty;
-		this._element.style.marginLeft = empty ? '0' : null;
+		this._element.style.marginLeft = empty ? '0' : '';
 	}
 
 	dispose(): void {
diff --git a/src/vs/base/browser/ui/progressbar/progressbar.ts b/src/vs/base/browser/ui/progressbar/progressbar.ts
index 19e16dfbe87..198d8e2310e 100644
--- a/src/vs/base/browser/ui/progressbar/progressbar.ts
+++ b/src/vs/base/browser/ui/progressbar/progressbar.ts
@@ -221,7 +221,7 @@ export class ProgressBar extends Disposable {
 
 	protected applyStyles(): void {
 		if (this.bit) {
-			const background = this.progressBarBackground ? this.progressBarBackground.toString() : null;
+			const background = this.progressBarBackground ? this.progressBarBackground.toString() : '';
 
 			this.bit.style.backgroundColor = background;
 		}
diff --git a/src/vs/base/browser/ui/tree/abstractTree.ts b/src/vs/base/browser/ui/tree/abstractTree.ts
index e0376d8a519..b34dd3936a7 100644
--- a/src/vs/base/browser/ui/tree/abstractTree.ts
+++ b/src/vs/base/browser/ui/tree/abstractTree.ts
@@ -780,8 +780,8 @@ class TypeFilterController<T, TFilterData> implements IDisposable {
 		const onDragEnd = () => {
 			this.positionClassName = positionClassName;
 			this.domNode.className = `monaco-list-type-filter ${this.positionClassName}`;
-			this.domNode.style.top = null;
-			this.domNode.style.left = null;
+			this.domNode.style.top = '';
+			this.domNode.style.left = '';
 
 			dispose(disposables);
 		};
diff --git a/src/vs/base/parts/quickopen/browser/quickOpenModel.ts b/src/vs/base/parts/quickopen/browser/quickOpenModel.ts
index 5e1b2154cc1..9f92529bdac 100644
--- a/src/vs/base/parts/quickopen/browser/quickOpenModel.ts
+++ b/src/vs/base/parts/quickopen/browser/quickOpenModel.ts
@@ -434,7 +434,7 @@ class Renderer implements IRenderer<QuickOpenEntry> {
 				}
 			} else {
 				DOM.removeClass(groupData.container, 'results-group-separator');
-				groupData.container.style.borderTopColor = null;
+				groupData.container.style.borderTopColor = '';
 			}
 
 			// Group Label
diff --git a/src/vs/editor/contrib/rename/renameInputField.ts b/src/vs/editor/contrib/rename/renameInputField.ts
index 1113144c6c4..a87899a71a1 100644
--- a/src/vs/editor/contrib/rename/renameInputField.ts
+++ b/src/vs/editor/contrib/rename/renameInputField.ts
@@ -89,14 +89,14 @@ export class RenameInputField implements IContentWidget, IDisposable {
 		const widgetShadowColor = theme.getColor(widgetShadow);
 		const border = theme.getColor(inputBorder);
 
-		this._inputField.style.backgroundColor = background ? background.toString() : null;
+		this._inputField.style.backgroundColor = background ? background.toString() : '';
 		this._inputField.style.color = foreground ? foreground.toString() : null;
 
 		this._inputField.style.borderWidth = border ? '1px' : '0px';
 		this._inputField.style.borderStyle = border ? 'solid' : 'none';
 		this._inputField.style.borderColor = border ? border.toString() : 'none';
 
-		this._domNode!.style.boxShadow = widgetShadowColor ? ` 0 2px 8px ${widgetShadowColor}` : null;
+		this._domNode!.style.boxShadow = widgetShadowColor ? ` 0 2px 8px ${widgetShadowColor}` : '';
 	}
 
 	private updateFont(): void {
diff --git a/src/vs/workbench/browser/parts/editor/editorDropTarget.ts b/src/vs/workbench/browser/parts/editor/editorDropTarget.ts
index 94597ec5c07..b5089f88f4f 100644
--- a/src/vs/workbench/browser/parts/editor/editorDropTarget.ts
+++ b/src/vs/workbench/browser/parts/editor/editorDropTarget.ts
@@ -85,7 +85,7 @@ class DropOverlay extends Themable {
 	protected updateStyles(): void {
 
 		// Overlay drop background
-		this.overlay.style.backgroundColor = this.getColor(EDITOR_DRAG_AND_DROP_BACKGROUND);
+		this.overlay.style.backgroundColor = this.getColor(EDITOR_DRAG_AND_DROP_BACKGROUND) || '';
 
 		// Overlay contrast border (if any)
 		const activeContrastBorderColor = this.getColor(activeContrastBorder);
diff --git a/src/vs/workbench/browser/parts/editor/editorPart.ts b/src/vs/workbench/browser/parts/editor/editorPart.ts
index a3dec299bc6..9f5b31c4f55 100644
--- a/src/vs/workbench/browser/parts/editor/editorPart.ts
+++ b/src/vs/workbench/browser/parts/editor/editorPart.ts
@@ -796,7 +796,7 @@ export class EditorPart extends Part implements IEditorGroupsService, IEditorGro
 	}
 
 	updateStyles(): void {
-		this.container.style.backgroundColor = this.getColor(editorBackground);
+		this.container.style.backgroundColor = this.getColor(editorBackground) || '';
 
 		const separatorBorderStyle = { separatorBorder: this.gridSeparatorBorder, background: this.theme.getColor(EDITOR_PANE_BACKGROUND) || Color.transparent };
 		this.gridWidget.style(separatorBorderStyle);
diff --git a/src/vs/workbench/browser/parts/editor/editorWidgets.ts b/src/vs/workbench/browser/parts/editor/editorWidgets.ts
index 6616272abb1..22ca587814e 100644
--- a/src/vs/workbench/browser/parts/editor/editorWidgets.ts
+++ b/src/vs/workbench/browser/parts/editor/editorWidgets.ts
@@ -75,9 +75,9 @@ export class FloatingClickWidget extends Widget implements IOverlayWidget {
 				this._domNode.style.color = foregroundColor.toString();
 			}
 
-			const borderColor = colors.contrastBorder ? colors.contrastBorder.toString() : null;
-			this._domNode.style.borderWidth = borderColor ? '1px' : null;
-			this._domNode.style.borderStyle = borderColor ? 'solid' : null;
+			const borderColor = colors.contrastBorder ? colors.contrastBorder.toString() : '';
+			this._domNode.style.borderWidth = borderColor ? '1px' : '';
+			this._domNode.style.borderStyle = borderColor ? 'solid' : '';
 			this._domNode.style.borderColor = borderColor;
 		}));
 
diff --git a/src/vs/workbench/browser/parts/editor/tabsTitleControl.ts b/src/vs/workbench/browser/parts/editor/tabsTitleControl.ts
index 2fc4adaf8db..9ff0ac17f9c 100644
--- a/src/vs/workbench/browser/parts/editor/tabsTitleControl.ts
+++ b/src/vs/workbench/browser/parts/editor/tabsTitleControl.ts
@@ -728,8 +728,8 @@ export class TabsTitleControl extends TitleControl {
 		const isActiveTab = isTab && !!editor && this.group.isActive(editor);
 
 		// Background
-		const noDNDBackgroundColor = isTab ? this.getColor(isActiveTab ? TAB_ACTIVE_BACKGROUND : TAB_INACTIVE_BACKGROUND) : null;
-		element.style.backgroundColor = isDND ? this.getColor(EDITOR_DRAG_AND_DROP_BACKGROUND) : noDNDBackgroundColor;
+		const noDNDBackgroundColor = isTab ? this.getColor(isActiveTab ? TAB_ACTIVE_BACKGROUND : TAB_INACTIVE_BACKGROUND) : '';
+		element.style.backgroundColor = (isDND ? this.getColor(EDITOR_DRAG_AND_DROP_BACKGROUND) : noDNDBackgroundColor) || '';
 
 		// Outline
 		const activeContrastBorderColor = this.getColor(activeContrastBorder);
@@ -879,7 +879,7 @@ export class TabsTitleControl extends TitleControl {
 
 		// Borders / Outline
 		const borderRightColor = (this.getColor(TAB_BORDER) || this.getColor(contrastBorder));
-		tabContainer.style.borderRight = borderRightColor ? `1px solid ${borderRightColor}` : null;
+		tabContainer.style.borderRight = borderRightColor ? `1px solid ${borderRightColor}` : '';
 		tabContainer.style.outlineColor = this.getColor(activeContrastBorder) || '';
 
 		// Settings
@@ -934,7 +934,7 @@ export class TabsTitleControl extends TitleControl {
 			// Container
 			addClass(tabContainer, 'active');
 			tabContainer.setAttribute('aria-selected', 'true');
-			tabContainer.style.backgroundColor = this.getColor(isGroupActive ? TAB_ACTIVE_BACKGROUND : TAB_UNFOCUSED_ACTIVE_BACKGROUND);
+			tabContainer.style.backgroundColor = this.getColor(isGroupActive ? TAB_ACTIVE_BACKGROUND : TAB_UNFOCUSED_ACTIVE_BACKGROUND) || '';
 
 			const activeTabBorderColorBottom = this.getColor(isGroupActive ? TAB_ACTIVE_BORDER : TAB_UNFOCUSED_ACTIVE_BORDER);
 			if (activeTabBorderColorBottom) {
@@ -964,8 +964,8 @@ export class TabsTitleControl extends TitleControl {
 			// Container
 			removeClass(tabContainer, 'active');
 			tabContainer.setAttribute('aria-selected', 'false');
-			tabContainer.style.backgroundColor = this.getColor(TAB_INACTIVE_BACKGROUND);
-			tabContainer.style.boxShadow = null;
+			tabContainer.style.backgroundColor = this.getColor(TAB_INACTIVE_BACKGROUND) || '';
+			tabContainer.style.boxShadow = '';
 
 			// Label
 			tabLabelWidget.element.style.color = this.getColor(isGroupActive ? TAB_INACTIVE_FOREGROUND : TAB_UNFOCUSED_INACTIVE_FOREGROUND);
diff --git a/src/vs/workbench/browser/parts/notifications/notificationsToasts.ts b/src/vs/workbench/browser/parts/notifications/notificationsToasts.ts
index d8087235f5e..863dd01c1c7 100644
--- a/src/vs/workbench/browser/parts/notifications/notificationsToasts.ts
+++ b/src/vs/workbench/browser/parts/notifications/notificationsToasts.ts
@@ -421,10 +421,10 @@ export class NotificationsToasts extends Themable {
 	protected updateStyles(): void {
 		this.mapNotificationToToast.forEach(t => {
 			const widgetShadowColor = this.getColor(widgetShadow);
-			t.toast.style.boxShadow = widgetShadowColor ? `0 0px 8px ${widgetShadowColor}` : null;
+			t.toast.style.boxShadow = widgetShadowColor ? `0 0px 8px ${widgetShadowColor}` : '';
 
 			const borderColor = this.getColor(NOTIFICATIONS_TOAST_BORDER);
-			t.toast.style.border = borderColor ? `1px solid ${borderColor}` : null;
+			t.toast.style.border = borderColor ? `1px solid ${borderColor}` : '';
 		});
 	}
 
diff --git a/src/vs/workbench/browser/parts/quickinput/quickInput.ts b/src/vs/workbench/browser/parts/quickinput/quickInput.ts
index ddb957fee79..24a0b6e3202 100644
--- a/src/vs/workbench/browser/parts/quickinput/quickInput.ts
+++ b/src/vs/workbench/browser/parts/quickinput/quickInput.ts
@@ -305,8 +305,8 @@ class QuickInput extends Disposable implements IQuickInput {
 		this.ui.inputBox.showDecoration(severity);
 		if (severity === Severity.Error) {
 			const styles = this.ui.inputBox.stylesForType(severity);
-			this.ui.message.style.backgroundColor = styles.background ? `${styles.background}` : null;
-			this.ui.message.style.border = styles.border ? `1px solid ${styles.border}` : null;
+			this.ui.message.style.backgroundColor = styles.background ? `${styles.background}` : '';
+			this.ui.message.style.border = styles.border ? `1px solid ${styles.border}` : '';
 			this.ui.message.style.paddingBottom = '4px';
 		} else {
 			this.ui.message.style.backgroundColor = '';
@@ -1511,16 +1511,16 @@ export class QuickInputService extends Component implements IQuickInputService {
 		if (this.ui) {
 			// TODO
 			const titleColor = { dark: 'rgba(255, 255, 255, 0.105)', light: 'rgba(0,0,0,.06)', hc: 'black' }[theme.type];
-			this.titleBar.style.backgroundColor = titleColor ? titleColor.toString() : null;
+			this.titleBar.style.backgroundColor = titleColor ? titleColor.toString() : '';
 			this.ui.inputBox.style(theme);
 			const quickInputBackground = theme.getColor(QUICK_INPUT_BACKGROUND);
-			this.ui.container.style.backgroundColor = quickInputBackground ? quickInputBackground.toString() : null;
+			this.ui.container.style.backgroundColor = quickInputBackground ? quickInputBackground.toString() : '';
 			const quickInputForeground = theme.getColor(QUICK_INPUT_FOREGROUND);
 			this.ui.container.style.color = quickInputForeground ? quickInputForeground.toString() : null;
 			const contrastBorderColor = theme.getColor(contrastBorder);
-			this.ui.container.style.border = contrastBorderColor ? `1px solid ${contrastBorderColor}` : null;
+			this.ui.container.style.border = contrastBorderColor ? `1px solid ${contrastBorderColor}` : '';
 			const widgetShadowColor = theme.getColor(widgetShadow);
-			this.ui.container.style.boxShadow = widgetShadowColor ? `0 5px 8px ${widgetShadowColor}` : null;
+			this.ui.container.style.boxShadow = widgetShadowColor ? `0 5px 8px ${widgetShadowColor}` : '';
 		}
 	}
 
diff --git a/src/vs/workbench/contrib/debug/browser/statusbarColorProvider.ts b/src/vs/workbench/contrib/debug/browser/statusbarColorProvider.ts
index 20d1d4a6a25..866505f7a91 100644
--- a/src/vs/workbench/contrib/debug/browser/statusbarColorProvider.ts
+++ b/src/vs/workbench/contrib/debug/browser/statusbarColorProvider.ts
@@ -66,7 +66,7 @@ export class StatusBarColorProvider extends Themable implements IWorkbenchContri
 
 		// Container Colors
 		const backgroundColor = this.getColor(this.getColorKey(STATUS_BAR_NO_FOLDER_BACKGROUND, STATUS_BAR_DEBUGGING_BACKGROUND, STATUS_BAR_BACKGROUND));
-		container.style.backgroundColor = backgroundColor;
+		container.style.backgroundColor = backgroundColor || '';
 		container.style.color = this.getColor(this.getColorKey(STATUS_BAR_NO_FOLDER_FOREGROUND, STATUS_BAR_DEBUGGING_FOREGROUND, STATUS_BAR_FOREGROUND));
 
 		// Border Color
diff --git a/src/vs/workbench/contrib/preferences/browser/keybindingWidgets.ts b/src/vs/workbench/contrib/preferences/browser/keybindingWidgets.ts
index dd0ea57af6d..578cc39ab59 100644
--- a/src/vs/workbench/contrib/preferences/browser/keybindingWidgets.ts
+++ b/src/vs/workbench/contrib/preferences/browser/keybindingWidgets.ts
@@ -183,7 +183,7 @@ export class DefineKeybindingWidget extends Widget {
 			if (colors.editorWidgetBackground) {
 				this._domNode.domNode.style.backgroundColor = colors.editorWidgetBackground.toString();
 			} else {
-				this._domNode.domNode.style.backgroundColor = null;
+				this._domNode.domNode.style.backgroundColor = '';
 			}
 			if (colors.editorWidgetForeground) {
 				this._domNode.domNode.style.color = colors.editorWidgetForeground.toString();
@@ -194,7 +194,7 @@ export class DefineKeybindingWidget extends Widget {
 			if (colors.widgetShadow) {
 				this._domNode.domNode.style.boxShadow = `0 2px 8px ${colors.widgetShadow}`;
 			} else {
-				this._domNode.domNode.style.boxShadow = null;
+				this._domNode.domNode.style.boxShadow = '';
 			}
 		}));
 
diff --git a/src/vs/workbench/contrib/preferences/browser/keybindingsEditor.ts b/src/vs/workbench/contrib/preferences/browser/keybindingsEditor.ts
index 0437702abf9..eea6c420e1c 100644
--- a/src/vs/workbench/contrib/preferences/browser/keybindingsEditor.ts
+++ b/src/vs/workbench/contrib/preferences/browser/keybindingsEditor.ts
@@ -401,13 +401,13 @@ export class KeybindingsEditor extends BaseEditor implements IKeybindingsEditor
 		const recordingBadge = DOM.append(container, DOM.$('.recording-badge.disabled'));
 		recordingBadge.textContent = localize('recording', "Recording Keys");
 		this._register(attachStylerCallback(this.themeService, { badgeBackground, contrastBorder, badgeForeground }, colors => {
-			const background = colors.badgeBackground ? colors.badgeBackground.toString() : null;
-			const border = colors.contrastBorder ? colors.contrastBorder.toString() : null;
-			const color = colors.badgeForeground ? colors.badgeForeground.toString() : null;
+			const background = colors.badgeBackground ? colors.badgeBackground.toString() : '';
+			const border = colors.contrastBorder ? colors.contrastBorder.toString() : '';
+			const color = colors.badgeForeground ? colors.badgeForeground.toString() : '';
 
 			recordingBadge.style.backgroundColor = background;
-			recordingBadge.style.borderWidth = border ? '1px' : null;
-			recordingBadge.style.borderStyle = border ? 'solid' : null;
+			recordingBadge.style.borderWidth = border ? '1px' : '';
+			recordingBadge.style.borderStyle = border ? 'solid' : '';
 			recordingBadge.style.borderColor = border;
 			recordingBadge.style.color = color ? color.toString() : null;
 		}));
diff --git a/src/vs/workbench/contrib/preferences/browser/preferencesEditor.ts b/src/vs/workbench/contrib/preferences/browser/preferencesEditor.ts
index ba32cf2dda9..2c8cfd12820 100644
--- a/src/vs/workbench/contrib/preferences/browser/preferencesEditor.ts
+++ b/src/vs/workbench/contrib/preferences/browser/preferencesEditor.ts
@@ -683,7 +683,7 @@ class PreferencesRenderersController extends Disposable {
 	}
 
 	private _updatePreference(key: string, value: any, source: ISetting, fromEditableSettings?: boolean): void {
-		const data: { [key: string]: any } = {
+		const data: { [key: string]: any; } = {
 			userConfigurationKeys: [key]
 		};
 
@@ -718,7 +718,7 @@ class PreferencesRenderersController extends Disposable {
 		this.telemetryService.publicLog('defaultSettingsActions.copySetting', data);
 	}
 
-	private _findSetting(filterResult: IFilterResult, key: string): { groupIdx: number, settingIdx: number, overallSettingIdx: number } | undefined {
+	private _findSetting(filterResult: IFilterResult, key: string): { groupIdx: number, settingIdx: number, overallSettingIdx: number; } | undefined {
 		let overallSettingIdx = 0;
 
 		for (let groupIdx = 0; groupIdx < filterResult.filteredGroups.length; groupIdx++) {
@@ -826,11 +826,7 @@ class SideBySidePreferencesWidget extends Widget {
 		this._register(attachStylerCallback(this.themeService, { scrollbarShadow }, colors => {
 			const shadow = colors.scrollbarShadow ? colors.scrollbarShadow.toString() : null;
 
-			if (shadow) {
-				this.editablePreferencesEditorContainer.style.boxShadow = `-6px 0 5px -5px ${shadow}`;
-			} else {
-				this.editablePreferencesEditorContainer.style.boxShadow = null;
-			}
+			this.editablePreferencesEditorContainer.style.boxShadow = shadow ? `-6px 0 5px -5px ${shadow}` : '';
 		}));
 
 		this.splitview.addView({
@@ -845,7 +841,7 @@ class SideBySidePreferencesWidget extends Widget {
 		this._register(focusTracker.onDidFocus(() => this._onFocus.fire()));
 	}
 
-	setInput(defaultPreferencesEditorInput: DefaultPreferencesEditorInput, editablePreferencesEditorInput: EditorInput, options: EditorOptions | undefined, token: CancellationToken): Promise<{ defaultPreferencesRenderer?: IPreferencesRenderer<ISetting>, editablePreferencesRenderer?: IPreferencesRenderer<ISetting> }> {
+	setInput(defaultPreferencesEditorInput: DefaultPreferencesEditorInput, editablePreferencesEditorInput: EditorInput, options: EditorOptions | undefined, token: CancellationToken): Promise<{ defaultPreferencesRenderer?: IPreferencesRenderer<ISetting>, editablePreferencesRenderer?: IPreferencesRenderer<ISetting>; }> {
 		this.getOrCreateEditablePreferencesEditor(editablePreferencesEditorInput);
 		this.settingsTargetsWidget.settingsTarget = this.getSettingsTarget(editablePreferencesEditorInput.getResource()!);
 		return Promise.all([