Fix typo.
Make DebugView and GraphView handle FLAnimatedImages with zero frames.

A performance improvement is coming that causes FLAnimatedImages to momentarily have zero frames while initially loading, DebugView and GraphView were causing crashes in this situation.
Add a seriously huge animated GIF for edge case testing.
Move slow work to a background thread.

Calling CGImageSourceGetCount is very slow for large GIFs. Loading only the poster frame synchronously on the main thread and deferring all other work make playback of these GIFs much faster.