The 'Write Your First App' main.dart but with an intentional error in place.

Your_First_App.dart

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

import 'package:catcher/catcher_plugin.dart';
import 'error_handler.dart';

// void main() => runApp(MyApp());

//void main() => ErrorHandler.runApp(MyApp());

void main()  {
  CatcherOptions debugOptions =
  CatcherOptions(DialogReportMode(), [ConsoleHandler(), ToastHandler()]);
  CatcherOptions releaseOptions = CatcherOptions(DialogReportMode(), [
    EmailManualHandler(["recipient@email.com"])
  ]);

  // Override the default 'ErrorWidget.builder'
  Catcher.addDefaultErrorWidget(showStacktrace: true);

  Catcher(MyApp(), debugConfig: debugOptions, releaseConfig: releaseOptions);
}

class MyApp extends StatelessWidget {
  // #docregion build
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      navigatorKey: Catcher.navigatorKey,
      title: 'Startup Name Generator',
      theme: ThemeData(
        primaryColor: Colors.white,
      ),
      home: RandomWords(),
    );
  }
}

class RandomWordsState extends State<RandomWords> {
  final _suggestions = <WordPair>[];
  final Set<WordPair> _saved = Set<WordPair>();
  final _biggerFont = const TextStyle(fontSize: 18.0);

  @override
  void initState() {
    super.initState();
    handler = ErrorHandler();
  }

  ErrorHandler handler;

  @override
  void dispose() {
    handler?.dispose();
    super.dispose();
  }

  Widget _buildSuggestions() {
    return ListView.builder(
        padding: const EdgeInsets.all(16.0),
        itemBuilder: /*1*/ (context, i) {
          if (i.isOdd) return Divider(); /*2*/

          final index = i ~/ 2; /*3*/
          if (index >= _suggestions.length) {
            _suggestions.addAll(generateWordPairs().take(10)); /*4*/
            //****** Clear the suggestions here. ******//
            _suggestions.clear();
          }
          //****** to cause an error here. ******//
          return _buildRow(_suggestions[index]);
        });
  }

  Widget _buildRow(WordPair pair) {
    final bool alreadySaved = _saved.contains(pair);
    return ListTile(
      title: Text(
        pair.asPascalCase,
        style: _biggerFont,
      ),
      trailing: Icon(
        alreadySaved ? Icons.favorite : Icons.favorite_border,
        color: alreadySaved ? Colors.red : null,
      ),
      onTap: () {
        setState(() {
          if (alreadySaved) {
            _saved.remove(pair);
          } else {
            _saved.add(pair);
          }
        });
      },
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Startup Name Generator'),
        actions: <Widget>[
          IconButton(icon: Icon(Icons.list), onPressed: _pushSaved),
        ],
      ),
      body: _buildSuggestions(),
    );
  }

  void _pushSaved() {
    Navigator.of(context).push(
      MaterialPageRoute<void>(
        // Add 20 lines from here...
        builder: (BuildContext context) {
          final Iterable<ListTile> tiles = _saved.map(
            (WordPair pair) {
              return ListTile(
                title: Text(
                  pair.asPascalCase,
                  style: _biggerFont,
                ),
              );
            },
          );
          final List<Widget> divided = ListTile.divideTiles(
            context: context,
            tiles: tiles,
          ).toList();

          return Scaffold(
            appBar: AppBar(
              title: Text('Saved Suggestions'),
            ),
            body: ListView(children: divided),
          );
        },
      ),
    );
  }
}

class RandomWords extends StatefulWidget {
  @override
  RandomWordsState createState() => RandomWordsState();
}