Dart/Flutter: Strings of element inside a List becomes empty when passing as an argument (Why??)

Strings of element inside a List becomes empty when passing as an argument. It was working before. I don't know what happened that it stopped working, and started passing empty.

I have a model called SubjectiveList, it is the list I am talking about.

class SubjectiveList {
  String id;
  String name;
  List<Item> items;
  SubjectiveList({this.id, this.name, this.items});
}

This list has the property items. What becomes empty is the properties inside the Item object.

class Item {
  String id;
  String name;
  Content content;

  Item({this.id, this.name, this.content});
}

On the debugger, The newList instance appears fine, with the object names (ps: the ID is okay to be null at this point because it will come from Firestore Database later)

Here is the code with the screenshots:

Future<dynamic> showListInfoDialog() {
    final userData = Provider.of<UserData>(context, listen: false);
    GlobalKey<FormState> _addListInfoFormKey = GlobalKey<FormState>();
    final ValueNotifier<int> tabIndex =
        Provider.of<ValueNotifier<int>>(context, listen: false);
    TempListViewModel tempList =
        Provider.of<TempListViewModel>(context, listen: false);

    return showDialog(
      context: context,
      child: SimpleDialog(
        title: Text("List Info"),
        children: <Widget>[
          Padding(
            padding: const EdgeInsets.all(defaultSpacing),
            child: Form(
              key: _addListInfoFormKey,
              child: Column(
                children: <Widget>[
                  TextFormField(
                    onChanged: (val) => tempList.setListName(val),
                    validator: (val) => val.isEmpty ? 'Write a name' : null,
                    decoration: InputDecoration(
                      prefixIcon: Icon(Icons.featured_play_list),
                      labelText: "List Name",
                    ),
                  ),
                  SizedBox(height: defaultSpacing),
                  SizedBox(
                    width: double.infinity,
                    child: RaisedButton(
                      child: Text("Create List"),
                      color: successColor,
                      onPressed: () {
                        if (_addListInfoFormKey.currentState.validate()) {
                          final newList = SubjectiveList(
                              name: tempList.list.name,
                              items: tempList.list.items);
                          DatabaseService(uid: userData.uid)
                              .addListToDatabase(newList); // <-- HERE
                          tempList.init();
                          tabIndex.value = 0;
                          Navigator.of(context).pop();
                        }
                      },
                    ),
                  )
                ],
              ),
            ),
          ),
        ],
      ),
    );
  }

And then it appears empty when coming to the function!!

Future addListToDatabase(SubjectiveList list) async { <-- HERE
    DocumentReference listDocument =
        await userDocument.collection('lists').add({'name': list.name});
    [...]
  }