Exception handling when the scrollbar touches the last frame of the behavior movie

[xuanma]

https://github.com/neuroethology/bentoMAT/blob/b228777aed54bf74209b61c98e646bdc0702c412/bento/gui/readBehMovieFrame.m#L33 When the scrollbar touches the last frame of the behavior movie, an error will be threw out saying "No more frames available to read from file" and the entire software will stop working.