fixes #58306

src/vs/workbench/browser/parts/titlebar/menubarControl.ts

@@ -415,6 +415,7 @@ export class MenubarControl extends Disposable {
 	}
 
 	private updateMnemonicVisibility(visible: boolean): void {
+		if (this.customMenus) {
 			this.customMenus.forEach(customMenu => {
 				if (customMenu.titleElement.children.length) {
 					let child = customMenu.titleElement.children.item(0) as HTMLElement;
@@ -424,6 +425,7 @@ export class MenubarControl extends Disposable {
 				}
 			});
 		}
+	}
 
 	private onRecentlyOpenedChange(): void {
 		this.windowService.getRecentlyOpened().then(recentlyOpened => {