Regression using last version(s) of ImageMagick

[Sean Enck]

On 2018-10-08, Sean Enck wrote:
> It appears importing an image has regressed (no longer works) against 
> kxstitch 2.1.1 when using the latest (well archlinux latest) versions of 
> image/libmagick. The current (not working version) in arch:
> > imagemagick-7.0.8.12-1-x86_64.pkg.tar.xz
> > libmagick-7.0.8.12-1-x86_64.pkg.tar.xz
> 
> I downgraded my versions to verify and import worked (no crash):
> > imagemagick-7.0.7.13-1-x86_64.pkg.tar.xz
> > libmagick-7.0.7.13-1-x86_64.pkg.tar.xz
> 
> The steps are:
> 1. open kxstitch
> 2. go to import image
> 3. select an image (any image, I haven't seen it work)
> 4. doesn't matter if you do anything before hitting "OK" when the image 
> would go to the normal grid
> 5. full crash, can provide a trace if there is anything special in kxstitch 
> or any specific tracing method is preferred.
> 
> Thanks for any help/insight,
> --Sean

I was able to do some digging and found the issue started around ImageMagick 
7.0.7.24 (works) -> 7.0.7.25 (broken). I traced it to the FlossScheme.cpp 
color matching where nullptr was being returned and I patched this in 
Arch using the referenced patch below.

https://aur.archlinux.org/cgit/aur.git/plain/0001-Change-nearest-color-lookup-logic-for-finding-floss-.patch?h=kxstitch