getAllPhotos method Null safety

Implementation

Future<void> getAllPhotos() async {
  emit(
    PhotosState.inProgress(
      currentPhotos: state.whenOrNull(success: (photos) => photos),
    ),
  );

  final result = await _getAllPhotos();

  emit(
    result.when(
      PhotosState.success,
      failure: PhotosState.failure,
    ),
  );
}