Memory corruption when optimizing GIF about gifsicle

[CyberShadow]

I don't know what the problem is. The global background variable gets set to 256, which I assume is not a valid value. It ends up at 256 because unmark_colors_2 sets .pixel to 256, which later is propagated to background at the end of initialize_optimizer. unmark_colors_2 also sets .haspixel to 0, but that gets set back to 1 in mark_used_colors. I can't make sense of the whole thing.

[kohler]

What a dumb bug! In an checkin that sped up optimization for images with many colors (cdd7f23), I stopped storing the 1st color in the output colormap. That is now fixed. (3901edf) I'll leave this for you to close (assuming that you stop seeing crashes). Thanks for the report.

[CyberShadow]

Yep, that fixed it, thanks!