Fix #52508 - error when opening/closing old prefs editor quickly

src/vs/workbench/parts/preferences/browser/preferencesEditor.ts

@@ -832,7 +832,7 @@ class SideBySidePreferencesWidget extends Widget {
 		this._register(focusTracker.onDidFocus(() => this._onFocus.fire()));
 	}
 
-	public setInput(defaultPreferencesEditorInput: DefaultPreferencesEditorInput, editablePreferencesEditorInput: EditorInput, options: EditorOptions, token: CancellationToken): TPromise<{ defaultPreferencesRenderer: IPreferencesRenderer<ISetting>, editablePreferencesRenderer: IPreferencesRenderer<ISetting> }> {
+	public setInput(defaultPreferencesEditorInput: DefaultPreferencesEditorInput, editablePreferencesEditorInput: EditorInput, options: EditorOptions, token: CancellationToken): TPromise<{ defaultPreferencesRenderer?: IPreferencesRenderer<ISetting>, editablePreferencesRenderer?: IPreferencesRenderer<ISetting> }> {
 		this.getOrCreateEditablePreferencesEditor(editablePreferencesEditorInput);
 		this.settingsTargetsWidget.settingsTarget = this.getSettingsTarget(editablePreferencesEditorInput.getResource());
 		return TPromise.join([
@@ -841,7 +841,7 @@ class SideBySidePreferencesWidget extends Widget {
 		])
 			.then(([defaultPreferencesRenderer, editablePreferencesRenderer]) => {
 				if (token.isCancellationRequested) {
-					return void 0;
+					return {};
 				}
 
 				this.defaultPreferencesHeader.textContent = defaultPreferencesRenderer && this.getDefaultPreferencesHeaderText((<DefaultSettingsEditorModel>defaultPreferencesRenderer.preferencesModel).target);