indexbox assertion error if image is clicked

[tobidelbruck]

indexbox is great, but if an image is specified, an AssertionError is generated by clicking the image, instead of nothing occuring (preferred) or returning None. A hack around this is:

    try:
        track_num = indexbox('What track do you want?', 'Tracks', tracks, image='media/all_tracks.png')
    except AssertionError as e:
        logger.warning(f'caught {e}: You must click one of the buttons, not the image')
        return None

Thanks for awesome project.