title: Unhandled Exception: type 'Null' is not a subtype of type 'int' when using login function
body: <p>the following method works fine, and i am able to register a new user on my parse based app backend</p>
  <pre><code>void doUserRegistration() async {
  
      final username = _textEditControllerEmailField.text.trim();
      final password = _textEditControllerPasswordField.text.trim();
      final user = ParseUser.createUser(username, password, username);
  
      var response = await user.signUp(allowWithoutEmail: true);
  
      if (response.success) {
  
        Navigator.of(context).pushNamedAndRemoveUntil('settingsPage', (route) =&gt; false);
      } else {
        showError(response.error!.message);
      }
    }
  </code></pre>
  <p>but this one fails with the error in the title above</p>
  <pre><code> void doUserLogin() async {
  
      final username = _textEditControllerEmailField.text.trim();
      final password = _textEditControllerPasswordField.text.trim();
      var user1 =  ParseUser.createUser(username, password, username);
  
      var response = await user1.login();
  
      if (response.success) {
  
        Navigator.of(context).pushNamedAndRemoveUntil('settingsPage', (route) =&gt; false);
      } else {
        showError(response.error!.message);
      }
    }
  </code></pre>
  <p>can anyone help me understand why ? i checked <a href="https://pub.dev/packages/parse_server_sdk_flutter" rel="nofollow noreferrer">https://pub.dev/packages/parse_server_sdk_flutter</a> this page and the login calls listed there don't work either</p>