Include invalid references as targets for find all references

For #146277

extensions/markdown-language-features/src/util/arrays.ts

@@ -15,4 +15,11 @@ export function equals<T>(one: ReadonlyArray<T>, other: ReadonlyArray<T>, itemEq
 	}
 
 	return true;
-}
+}
+
+/**
+ * @returns New array with all falsy values removed. The original array IS NOT modified.
+ */
+export function coalesce<T>(array: ReadonlyArray<T | undefined | null>): T[] {
+	return <T[]>array.filter(e => !!e);
+}