tileAnim does not work for negative offsets

[amirgamil]

Hi, I spent an hour today trying to get tileAnim to work for two tiles on the same row e.g. [a, b] but starting on b then moving back to A with animX = -1 This led to some weird behavior where the animation loaded an incorrect tile, I changed it to start at a with animX = 1 and it worked fine, but thought I'd open the issue for future reference.

[jjhesk]

make a test case for studying