Generator should not remove nullability from lists

[nirinchev]

When generating a model like

class _Foo {
    late List<int?> ints;
}

The generator succeeds but removes the nullability of the int? argument to my list:

class Foo extends _Foo{
  @override
  RealmList<int> get ints =>
      RealmObject.get<int>(this, 'ints') as RealmList<int>;
}

[dotjon0]

We second this.