#406 InvalidColormapIndex exception on GIFs

[Tianyu Lang]

GIF files get InvalidColormapIndex exception when GM identifies them.
These GIF files can be viewed on Chrome and Firefox. They can be transcoded to mp4 with FFMPEG. And they can also be identified with Gifsicle.

I think these GIFs might have a problem but I also think GM should loosen the criteria to handle real world GIFs.

Maybe log the error instead of throwing an exception in MagickConstrainColormapIndex in colormap.c

[Bob Friesenhahn]

Please archive and re-upload your sample files in a tarball or zip archive. SourceForge re-writes all JPEG, GIF, and PNG files which are uploaded. This often removes the problem from the files.

[Tianyu Lang]

Sorry. Here is the zipped version.