Error: `type 'null' is not a subtype of type String in type cast` while running local API in flutter device

I have a local flask api with a Get method that runs at http://127.0.0.1:5000/diario/aluno/240, which get one student at a time from a local database that I have. I want to run it on my device using Flutter on Visual Studio Code, but I am getting this error, which is displayed on my flutter app (running on my device):

type ‘null’ is not a subtype of type String in type cast.

I never get this error when I use similar (I would say equal) code when I fetch data from the internet. The rest of the app works fine on my device, but every method from my flask API just don’t work – this is just a simplified example.

import 'dart:async';
import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;

Future<Student> fetchStudent() async {
  final response = await http.get(Uri.parse('http://127.0.0.1:5000/diario/aluno/240'));
  if (response.statusCode == 200) { 
    return Student.fromJson(jsonDecode(response.body) as Map<String, dynamic>);
  } else {    
    throw Exception('Failed to load album');
  }
}
class Student {
  final String name;

const Student({
  required this.name 
});

factory Student.fromJson(Map<String, dynamic>json) {
  return Student(
    name: json['nome'] as String
  );
}
}
void main() => runApp(const MyApp());
class MyApp extends StatefulWidget {
  const MyApp({super.key});

  @override
  State<MyApp> createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
  late Future<Student> futureStudent;

@override
void initState() {
    super.initState();
    futureStudent = fetchStudent();
  }
@override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: "Fetch Student Api",
      home: Scaffold(
        appBar: AppBar(
          title: Text("Show students"),          
        ),
        body: Center(
          child: FutureBuilder<Student>(
            future: futureStudent,
            builder: ((context, snapshot) {
              if (snapshot.hasData) {
                return Text(snapshot.data!.name);
              } else if (snapshot.hasError) {
                return Text('${snapshot.error}');
              } 
              return const CircularProgressIndicator();
            }
          ),
        ),

      ), 


    )
    );     
     
  }
}

I tried to add name: json['nome'] as String? ?? 'there is no such name', but then the app never shows the real value from the database. Is there anyone who ever runs a local api using Flutter and has faced such problem? I thought it could be a problem of running on different ports too, so I tried adb reverse tcp:5000 tcp:5000, so the machine and my cellphone could run in the same port, but I still get the same error.