Gif frame cutting issues [WIP]

For https://assembly.com/firesize/bounties/27

This is a pretty YOLO first cut of addressing the bug where gifs stop working. Did some refactoring to find the right place to put the code, but I'm not happy with the error handling (ie in a bunch of cases I ignore errors, and don't log very much) and there's still a bit too much duplication.

Appreciate feedback on if this is on the right track.