[Firebase/Core][I-COR000005] No app has been configured yet

I already tried this post's all solutions, I'm using

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(...)
}

But I still see this error in my console:

8.9.0 - [Firebase/Core][I-COR000005] No app has been configured yet.

I tested it on both a simulator and a real device. However, all Firebase operations are working as expected.