error: [firebase_auth/unknown] Given String is empty or null

I don't know i can't create user with email and password to firebase Here is my error

I am a newbie to flutter and firebase and i don't know why

D/EGL_emulation( 9585): eglMakeCurrent: 0xb1386320: ver 2 0 (tinfo 0xb1383e20)
I/art     ( 9585): Do partial code cache collection, code=16KB, data=30KB
I/art     ( 9585): After code cache collection, code=14KB, data=29KB
I/art     ( 9585): Increasing code cache capacity to 128KB
3
D/InputConnectionAdaptor( 9585): The input method toggled cursor monitoring on
I/art     ( 9585): Do partial code cache collection, code=49KB, data=62KB
I/art     ( 9585): After code cache collection, code=49KB, data=62KB
I/art     ( 9585): Increasing code cache capacity to 256KB
I/flutter ( 9585): dat@gmail.com
I/flutter ( 9585): error: [firebase_auth/unknown] Given String is empty or null

Here is my code with firebase --------

class _AuthScreenState extends State<AuthScreen> {
  FirebaseAuth auth = FirebaseAuth.instance;
  void _SubmiyAuthForm(
      String email, String password, String username, bool isLogin) async {
    UserCredential authResult;
    try {
      if (isLogin) {
        authResult = await auth.signInWithEmailAndPassword(
            email: email, password: password);
      } else {
        authResult = await auth.createUserWithEmailAndPassword(
            email: email, password: password);
      }
    } on PlatformException catch (e) {
      // TODO
      var message = 'An error occured , please check  ';
      if (e.message != null) {
        message = e.message!;
      }
      Scaffold.of(context).showBottomSheet(
        (context) => SnackBar(
          content: Text(message),
          backgroundColor: Theme.of(context).errorColor,
        ),
      );
    } catch (E) {
      print('error: ' + E.toString());
    }
  }