Returning none insted of empty FrameContainer in preprocessor Wrapper
This update returns
None instead of empty FrameContainer in the preprocessor Wrapper class for an extreme case (for example, wrapped preprocessor returned
None for all frames in video for some reasons).
Works well with
--allow-missing-files option, because preprocessed file will not be written in this case.
Currently, empty FrameContainer is written to file, which might cause an error in the Extractor, if not handled. Also, added the test for this case.
@ageorge, can be useful for you as-well.