Also allow padding at the end of ctts boxes

[torokati44]

This was necessary to successfully parse the following file:
https://www.mea-culpa.at/02_videos/gesch_175_580x432px_12fps_300kbit.f4v

It has 7080 bytes of extra stuff in its ctts box after the given number of sample counts and offsets.

Other media players and demuxers (like VLC or MP4Box.js) had no problem with this particular file.

I copied the call and comment from other similar box reader functions nearby.

[kinetiknz]

Thanks! This seems reasonable, but I think it'd be good to only allow this when the parser is not in strict mode. I've adjusted your change to account for that and landed it in 49fc621 and 214b5ac.