запустить Flutter No Null Safety
flutter run --no-sound-null-safety
Zion
flutter run --no-sound-null-safetyflutter build apk --release --no-sound-null-safetydart pub outdated --mode=null-safetyTo Work Without Null Safety
Fix:
https://stackoverflow.com/questions/65302065/turn-off-null-safety-for-previous-flutter-project