flutter_cupertino_date_picker >=0.0.2 which doesn't support null safety from Dart SDK version is 3.0.3

[JY-1024]

Because first_flutter_app depends on flutter_cupertino_date_picker >=0.0.2 which doesn't support null safety, version solving failed.

The lower bound of "sdk: '>=1.19.0 <3.0.0'" must be 2.12.0 or higher to enable null safety.
For details, see https://dart.dev/null-safety
exit code 1