[firebase_auth_platform_interface] - Expected String got Null, when calling GoogleAuthProvider.credential(...) in google_auth.dart

[NeilFawcett1]

Latest Flutter, firebase, etc. Flutter Doctor fine. Applied recent fixes for the JS interop migration, which has fixed getIdToken and can now sign in without this error with username and password. But, the following code throws the string/null error:

                                                  final credential = GoogleAuthProvider
                                                      .credential(
                                                    accessToken: googleAuth?.accessToken,
                                                    idToken: googleAuth?.idToken,
                                                  );

Sorry, should say, this error is on Web. Works fine on Android.