fix: object has been destroyed

receive an error from webContents saying the object has been destroyed when executing the line
win.webContents.off('destroyed', disposable);

we can't unsubscribe once it's already destroyed

index.js

@@ -374,9 +374,9 @@ export default function contextMenu(options = {}) {
 		const disposeMenu = create(win, options);
 
 		const disposable = () => {
-			win.webContents.off('destroyed', disposable);
 			disposeMenu();
 		};
+		win.webContents.off('destroyed', disposable);
 
 		if (win.once !== undefined) { // Support for BrowserView
 			win.webContents.once('destroyed', disposable);