Remove extra null checks in coalesce

The type system should catch these now

src/vs/base/common/arrays.ts

@@ -293,12 +293,9 @@ function topStep<T>(array: ReadonlyArray<T>, compare: (a: T, b: T) => number, re
 }
 
 /**
- * @returns a new array with all falsy values removed. The original array IS NOT modified.
+ * @returns New array with all falsy values removed. The original array IS NOT modified.
  */
 export function coalesce<T>(array: ReadonlyArray<T | undefined | null>): T[] {
-	if (!array) {
-		return array;
-	}
 	return <T[]>array.filter(e => !!e);
 }
 
@@ -306,9 +303,6 @@ export function coalesce<T>(array: ReadonlyArray<T | undefined | null>): T[] {
  * Remove all falsey values from `array`. The original array IS modified.
  */
 export function coalesceInPlace<T>(array: Array<T | undefined | null>): void {
-	if (!array) {
-		return;
-	}
 	let to = 0;
 	for (let i = 0; i < array.length; i++) {
 		if (!!array[i]) {