GSImageMagickImageRep problems

[rmottola]

while investigating https://github.com/gnustep/apps-gworkspace/pull/20, I installed image magick and enabled support for it.

A small local patch is needed to support v7 (will try to insert version detection, since most OS has 6 or 7 available).

Several issues arise from GWorkspace now which needs to be analyzed, since they don't happen without IM support enabled.

When loading a PDF:

2023-12-12 09:19:08.875 GWorkspace[638:644] ImageMagick: zero-length blob not permitted `' @ error/blob.c/BlobToImage/450
2023-12-12 09:19:08.883 GWorkspace[638:638] ImageViewer: trying to display inconsistent image

2023-12-12 09:24:14.112 GWorkspace[638:644] ImageMagick: delegate library support not built-in `/tmp/magick-kjld8bf6U-7gHFW182cAJkuNv6amEkms' (XML) @ error/profile.c/ValidateXMPProfile/1943

But it also try to load an HTML

2023-12-12 09:26:02.549 GWorkspace[638:644] ImageMagick: zero-length blob not permitted `' @ error/blob.c/BlobToImage/450
2023-12-12 09:26:02.571 GWorkspace[638:638] ImageViewer: trying to display inconsistent image

[rmottola]

I add to this that I discovered than when I have ImageMagick support enabled, even opening a JPG image causes an application crash. By recompiling GUI without ImageMagick support, the same test file opens. Test with classic ImageMagick 6.9, which the existing code should support and was written for.