Possible issue with animated GIFs

[abonander]

I don't have the error message on hand (wasn't much use anyways), but it was an index out of bounds error when iterating the pixels of an image. For some reason, the internal vector length of the ImageBuf did not match width * height and so the iterator was going past the end. I was able to reduce the problem domain to certain animated GIFs, though I cannot provide the images I used for personal reasons.

[nwin]

duplicate of #91 I guess should be fixed soon.