Bonjour
Avec TNG, j'ai les erreurs qui s'affichent avec vos 2 galeries

'package:flutter/src/material/dropdown.dart':Failed assertion: line 892 pos 15: items == null || items.isEmpty || value == null ||
items.where((dropdownMenuItem<T> item) {return item.value ==value;}).length ==1': there should be exactly one item with [DropdownButton]s value:optimal.
Either zero or 2 or more[DropdownButton]s were detected with the same value
See also also: https ://flutter.dev/docs/testing/errors

A très vite