Flutter – Exception type 'Null' is not a subtype of type 'Map<dynamic, dynamic>'

In my code I have the part where I manage the state of the authentication in order to be able to add or not the user information however I have an exception which is thrownyour text

InitScreen.dart

`

class InitScreen extends StatefulWidget {
  const InitScreen({Key? key}) : super(key: key);

  @override
  _InitScreenState createState() => _InitScreenState();
}

class _InitScreenState extends State<InitScreen> {
  bool? _redirect;
  String? _redirectURL;

  Future<bool> _checkAuthStatus(BuildContext ctx) async {
    try {
      User? currentUser = FirebaseAuth.instance.currentUser;
      print('currentUser: $currentUser');
      if (currentUser == null) {
        _redirect = true;
        _redirectURL = "/login";
        print("Je suis revenue");
        return true;
      }
      print("--------------------");
      UserDatabaseService databaseService = UserDatabaseService();
      print("databaseService: $databaseService");
      print("currentUser.uid: ${currentUser.uid}");
      UserModel user = await databaseService.getUser(currentUser.uid);
      print("user: $user");
      if (user == null) {
        _redirect = true;
        _redirectURL = "/userinfo";
        return true;
      }
      print('/home');
      _redirectURL = "/home";
      _redirect = true;
      return true;
    } catch (err) {
      print("Dans le catch ******* $err");
      return false;
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
            FutureBuilder<bool>(
              future: _checkAuthStatus(context),
              builder: (BuildContext c, AsyncSnapshot<bool> snapshot) {
                print("InitState a retourné: ${snapshot.data}");
                if (snapshot.hasData && snapshot.data!) {
                  print("InitState a retourné: ${snapshot.data}");
                  Future.delayed(const Duration(milliseconds: 250), () {
                    print("Redirect: $_redirect $_redirectURL  |");
                    if (_redirect == true) {
                      Application.router.navigateTo(
                        context,
                        _redirectURL!,
                        replace: true,
                      );
                    }
                  });
                  return Container();
                } else if (snapshot.hasError) {
                  print(snapshot.error);
                  return Text(
                    "Authentication Error",
                    style: TextStyle(
                      fontFamily: 'Varela',
                      fontSize: 28,
                      fontWeight: FontWeight.w300,
                      color: Colors.white,
                    ),
                  );
                } else {
                  return Column(
                    children: [
                      // Ajoutez ici les widgets que vous souhaitez afficher
                    ],
                  );
                }
              },
            ),
            CircularProgressIndicator(
              backgroundColor: Colors.white,
              valueColor: AlwaysStoppedAnimation<Color>(
                Color.fromARGB(255, 247, 124, 23),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

 Future<UserModel> getUser(String id) async {
    DocumentSnapshot snapshot = await _db.collection('users').doc(id).get();
    
    return UserModel.fromSnapshot(snapshot);
  }

`class UserModel {

factory UserModel.fromSnapshot(DocumentSnapshot document) {
final Map data = document.data();
return UserModel(
userId: document.id,
email: data[’email’] ?? ‘Neant’,
fullName: data[‘fullName’] ?? ‘Neant’,
phoneNo: data[‘phoneNo’],
fieldId: data[‘fieldId’],
age: data[‘age’],
city: data[‘city’],
imageUrl: data[‘imageUrl’],
location: data[‘location’],
phone: data[‘phone’],
cdiNo: data[‘cdiNo’],
);
}
}`

I am looking for a solution in order to be able to access my /home

I have this exception
type ‘Null’ is not a subtype of type ‘Map<dynamic, dynamic>’
I provided here the function of my User class also the GetUser function and the InitScreen class