onError method
Called whenever an error occurs and notifies BlocObserver.onError.
Note: super.onError should always be called last.
@override
void onError(Object error, StackTrace stackTrace) {
  // Custom onError logic goes here
  // Always call super.onError with the current error and stackTrace
  super.onError(error, stackTrace);
}
Implementation
@protected
@mustCallSuper
void onError(Object error, StackTrace stackTrace) {
  // ignore: invalid_use_of_protected_member
  _blocObserver.onError(this, error, stackTrace);
}