Flutter Typography Toggle Assert Issue

main.dart

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatefulWidget {
  const MyApp({super.key});
  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  ThemeMode themeMode = ThemeMode.light;
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Typography theme toggle issue',
      debugShowCheckedModeBanner: false,
      themeMode: themeMode,
      theme: ThemeData(
          brightness: Brightness.light,
          typography: Typography.material2021(platform: defaultTargetPlatform)),
      darkTheme: ThemeData(
        brightness: Brightness.dark,
        typography: Typography.material2018(platform: defaultTargetPlatform),
      ),
      home: Scaffold(
        body: Center(
          child: HomePage(
            darkMode: themeMode == ThemeMode.dark,
            onChangedDarkMode: (bool value) {
              setState(() {
                if (value) {
                  themeMode = ThemeMode.dark;
                } else {
                  themeMode = ThemeMode.light;
                }
              });
            },
          ),
        ),
      ),
    );
  }
}

class HomePage extends StatelessWidget {
  const HomePage(
      {super.key, required this.darkMode, required this.onChangedDarkMode});
  final bool darkMode;
  final ValueChanged<bool> onChangedDarkMode;

  @override
  Widget build(BuildContext context) {
    return ListView(
      children: [
        Padding(
          padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 8.0),
          child: Text(
            'Typography theme toggle issue',
            style: Theme.of(context).textTheme.headlineSmall,
          ),
        ),
        SwitchListTile(
          title: const Text('Use dark mode'),
          value: darkMode,
          onChanged: onChangedDarkMode,
        ),
      ],
    );
  }
}