Fix types on CopyPasteController.get (#200600)

Fixes #200597

Author: mjbvz

src/vs/editor/contrib/clipboard/browser/clipboard.ts

@@ -229,7 +229,7 @@ if (PasteAction) {
 		if (focusedEditor && focusedEditor.hasTextFocus()) {
 			const result = focusedEditor.getContainerDomNode().ownerDocument.execCommand('paste');
 			if (result) {
-				return CopyPasteController.get(focusedEditor).finishedPaste();
+				return CopyPasteController.get(focusedEditor)?.finishedPaste() ?? Promise.resolve();
 			} else if (platform.isWeb) {
 				// Use the clipboard service if document.execCommand('paste') was not successful
 				return (async () => {

src/vs/editor/contrib/dropOrPasteInto/browser/copyPasteController.ts

@@ -51,8 +51,8 @@ export class CopyPasteController extends Disposable implements IEditorContributi
 
 	public static readonly ID = 'editor.contrib.copyPasteActionController';
 
-	public static get(editor: ICodeEditor): CopyPasteController {
-		return editor.getContribution<CopyPasteController>(CopyPasteController.ID)!;
+	public static get(editor: ICodeEditor): CopyPasteController | null {
+		return editor.getContribution<CopyPasteController>(CopyPasteController.ID);
 	}
 
 	private readonly _editor: ICodeEditor;