NoSuchMethodError (NoSuchMethodError: The getter 'uid' was called on null - flutter

Question

I am new to flutter and fairly new to Firebase. I have created or I should say, followed a tutorial on how to create a Login/Register Page using Firebase as the backend. Everything works fine, except the fact that when I restart my application and enter an account already created I get the error from the title. NoSuchMethodError (NoSuchMethodError: The getter 'uid' was called on null. Receiver: null Tried calling: uid)
Here is the link to the tutorial I have followed.
https://www.freecodespot.com/blog/flutter-login-and-registration-using-firebase/#Logindart_Source_Code
After that, the application freezes, so I restart it and it shows I am logged in.
P.S. Creating a new account, and trying to log in works. Trying to Log In into an existing account seems to be the problem, but after restarting the app, it works. Sorry for any spelling errors, english is not my first language.
Error on line 91.
import '/models/loginuser.dart';
import '/services/auth.dart';
import 'package:flutter/material.dart';
class Login extends StatefulWidget {
final Function? toggleView;
Login({this.toggleView});
#override
State<StatefulWidget> createState() {
return _Login();
}
}
class _Login extends State<Login> {
bool _obscureText = true;
final _email = TextEditingController();
final _password = TextEditingController();
final GlobalKey<FormState> _formKey = GlobalKey<FormState>();
final AuthSerice _auth = AuthSerice();
#override
Widget build(BuildContext context) {
final emailField = TextFormField(
controller: _email,
autofocus: false,
validator: (value) {
if (value != null) {
if (value.contains('#') && value.endsWith('.com')) {
return null;
}
return 'Enter an email address!';
}
},
decoration: InputDecoration(
contentPadding: const EdgeInsets.fromLTRB(20.0, 15.0, 20.0, 15.0),
hintText: "Email",
border:
OutlineInputBorder(borderRadius: BorderRadius.circular(32.0))));
final passwordField = TextFormField(
obscureText: _obscureText,
controller: _password,
autofocus: false,
validator: (value) {
if (value == null || value.trim().isEmpty) {
return 'This field is required!';
}
if (value.trim().length < 6) {
return 'Password must be at least 6 characters in length!';
}
// Return null if the entered password is valid
return null;
},
decoration: InputDecoration(
contentPadding: const EdgeInsets.fromLTRB(20.0, 15.0, 20.0, 15.0),
hintText: "Password",
suffixIcon: IconButton(
icon:
Icon(_obscureText ? Icons.visibility : Icons.visibility_off),
onPressed: () {
setState(() {
_obscureText = !_obscureText;
});
},
),
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(32.0),
)));
final txtbutton = TextButton(
onPressed: () {
widget.toggleView!();
},
child: const Text('Register here!'));
final loginEmailPasswordButon = Material(
elevation: 5.0,
borderRadius: BorderRadius.circular(30.0),
color: Theme.of(context).primaryColor,
child: MaterialButton(
minWidth: MediaQuery.of(context).size.width,
padding: const EdgeInsets.fromLTRB(20.0, 15.0, 20.0, 15.0),
onPressed: () async {
if (_formKey.currentState!.validate()) {
dynamic result = await _auth.signInEmailPassword(LoginUser(email: _email.text,password: _password.text));
if (result.uid == null) { //null means unsuccessfull authentication
showDialog(
context: context,
builder: (context) {
return AlertDialog(
content: Text(result.code),
);
});
}
}
},
child: Text(
"Log in",
style: TextStyle(color: Theme.of(context).primaryColorLight),
textAlign: TextAlign.center,
),
),
);
return Scaffold(
resizeToAvoidBottomInset: false,
appBar: AppBar(
title: const Text('LOGIN VXS FARMING'),
backgroundColor: Theme.of(context).primaryColor,
centerTitle: true,
),
body: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Form(
key: _formKey,
child: Padding(
padding: const EdgeInsets.all(16.0),
child: Column(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
emailField,
const SizedBox(height: 25.0),
passwordField,
txtbutton,
const SizedBox(height: 35.0),
loginEmailPasswordButon,
const SizedBox(height: 15.0),
],
),
),
),
],
),
);
}
}
Commenting the if from line 91, there is no crash and the log in happens, but if I enter a wrong email, or password, there is no prompt saying that. It just clicks the button and nothing happens.