Fix null error in example (#433)
Fix null error in example (#433)


firebase/flutterfire,firebase/flutterfire,googleads/googleads-mobile-flutter,googleads/googleads-mobile-flutter,firebase/flutterfire,googleads/googleads-mobile-flutter,firebase/flutterfire,firebase/flutterfire,firebase/flutterfire,firebase/flutterfire,firebase/flutterfire,firebase/flutterfire,firebase/flutterfire,googleads/googleads-mobile-flutter