@require parameter '#' can't have a value of 'null' because of its type

Hello everybody working on a project and get this code from a repo and have some types errors and I cant understand them because I cant have the knowledge to solve and I didnt find nothing on google about these errors.

The problem is the @require this.#property and error as null value. I cant understand the problem, can explain me the problem?

Home Widget

class Home extends StatelessWidget {
  const Home({
    Key? key,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Stack(
        children: [
          Container(
            decoration: const BoxDecoration(
              gradient: LinearGradient(
                begin: Alignment.topCenter,
                end: Alignment.bottomCenter,
                colors: [
                  AppColors.backgroundFadedColor,
                  AppColors.backgroundColor,
                ],
                stops: [0.0, 1],
              ),
            ),
          ),
          SafeArea(
            child: _TodoListContent(
              todos: fakeData,
            ),
          ),
          const Align(
            alignment: Alignment.bottomRight,
            child: AddTodoButton(),
          )
        ],
      ),
    );
  }
}

class _TodoListContent extends StatelessWidget {
  const _TodoListContent({
    Key? key,
    @required this.todos,
  }) : super(key: key);

  final List<Todo> todos;

  @override
  Widget build(BuildContext context) {
    return ListView.builder(
      itemCount: todos.length,
      padding: const EdgeInsets.all(16),
      itemBuilder: (context, index) {
        final _todo = todos[index];
        return _TodoCard(todo: _todo);
      },
    );
  }
}

class _TodoCard extends StatelessWidget {
  const _TodoCard({
    Key? key,
    @required this.todo,
  }) : super(key: key);

  final Todo todo;

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: () {
        Navigator.of(context).push(
          HeroDialogRoute(
            builder: (context) => Center(
              child: _TodoPopupCard(todo: todo),
            ),
          ),
        );
      },
      child: Hero(
        tag: todo.id,
        child: Padding(
          padding: const EdgeInsets.symmetric(vertical: 8.0),
          child: Material(
            color: AppColors.cardColor,
            borderRadius: BorderRadius.circular(12),
            child: Padding(
              padding: const EdgeInsets.all(8.0),
              child: Column(
                children: <Widget>[
                  _TodoTitle(title: todo.description),
                  const SizedBox(
                    height: 8,
                  ),
                  if (todo.items.length != 0) ...[
                    const Divider(),
                    _TodoItemsBox(items: todo.items),
                  ]
                ],
              ),
            ),
          ),
        ),
      ),
    );
  }
}

class _TodoTitle extends StatelessWidget {
  const _TodoTitle({
    Key? key,
    @required this.title,
  }) : super(key: key);

  final String title;

  @override
  Widget build(BuildContext context) {
    return Text(
      title,
      style: const TextStyle(fontWeight: FontWeight.bold, fontSize: 16),
    );
  }
}

class _TodoPopupCard extends StatelessWidget {
  const _TodoPopupCard({Key key, this.todo}) : super(key: key);
  final Todo todo;

  @override
  Widget build(BuildContext context) {
    return Hero(
      tag: todo.id,
      child: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Material(
          borderRadius: BorderRadius.circular(16),
          color: AppColors.cardColor,
          child: SizedBox(
            child: Padding(
              padding: const EdgeInsets.all(16.0),
              child: SingleChildScrollView(
                child: Column(
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    _TodoTitle(title: todo.description),
                    const SizedBox(
                      height: 8,
                    ),
                    if (todo.items.length != 0) ...[
                      const Divider(),
                      _TodoItemsBox(items: todo.items),
                    ],
                    Container(
                      margin: const EdgeInsets.all(8),
                      decoration: BoxDecoration(
                        color: Colors.black12,
                        borderRadius: BorderRadius.circular(8),
                      ),
                      child: const TextField(
                        maxLines: 8,
                        cursorColor: Colors.white,
                        decoration: InputDecoration(
                            contentPadding: EdgeInsets.all(8),
                            hintText: 'Write a note...',
                            border: InputBorder.none),
                      ),
                    ),
                  ],
                ),
              ),
            ),
          ),
        ),
      ),
    );
  }
}

class _TodoItemsBox extends StatelessWidget {
  const _TodoItemsBox({
    Key? key,
    @required this.items,
  }) : super(key: key);

  final List<Item> items;

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        for (final item in items) _TodoItemTile(item: item),
      ],
    );
  }
}

class _TodoItemTile extends StatefulWidget {
  const _TodoItemTile({
    Key? key,
    @required this.item,
  }) : super(key: key);

  final Item item;

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

class _TodoItemTileState extends State<_TodoItemTile> {
  void _onChanged(bool val) {
    setState(() {
      widget.item.completed = val;
    });
  }

  @override
  Widget build(BuildContext context) {
    return ListTile(
      leading: Checkbox(
        onChanged: _onChanged,
        value: widget.item.completed,
      ),
      title: Text(widget.item.description),
    );
  }
}

On classes properties @required this.# error: The parameter '#' can't have a value of 'null' because of its type, but the implicit default value is 'null'. Try adding either an explicit non-'null' default value or the 'required' modifier.

Models file

import 'package:meta/meta.dart';

class Todo {
  const Todo({
    @required this.id,
    @required this.description,
    this.items,
  });

  final String id;
  final String description;
  final List<Item> items;
}

class Item {
  Item({
    @required this.id,
    this.description = '',
    this.completed = false,
  });

  final String id;
  final String description;
  bool completed;
}

On code

Todo
@required this.id,
@required this.description,
this.items,

and

Item
@required this.id,

error: The parameter '#' can't have a value of 'null' because of its type, but the implicit default value is 'null'. Try adding either an explicit non-'null' default value or the 'required' modifier.