Hi I am trying this piece of code and whenever I try to open and select something from the menù I get this error:

Exception has occurred.
_AssertionError ('package:flutter/src/rendering/object.dart': Failed assertion: line 3345 pos 14: 'renderer.parent != null': is not true.)

This is where I copied and pasted the code:

class test extends StatefulWidget{
  const test({super.key, required this.title});
  final String title;
  @override
  State<test> createState() => _testState();
}
const List<String> list = <String>['One', 'Two', 'Three', 'Four'];
class _testState extends State<test>{
  String dropdownValue = list.first;
  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: Scaffold(
        body: CustomScrollView(
          slivers: <Widget>[
            SliverAppBar(
              //...
            ),
            SliverFillRemaining(
              child: Align(
                alignment: Alignment.center,
                //2 SingleChildScrollView one with Axis.vertical and another one with Axis.horizontal
                //column
                //inside the column this:
                DropdownMenu<String>(
                  initialSelection: list.first,
                  onSelected: (String? value) {
                    setState(() {
                      dropdownValue = value!;
                    });
                  },
                  dropdownMenuEntries: 
                  list.map<DropdownMenuEntry<String>>((String value) {
                    return DropdownMenuEntry<String>(value: value, label: value);
                  }).toList(),
                );
              )
            )
          ]
        )
      )
    );
  }
}

I tried to delete the 2 SingleChildScrollView and everything works but I need them in order to not get an overflowed bottom since I have inside the column other elements beside this DropDownMenu. What can I do?