ImageMagick has Division-by-Zero in YUV sampling factor validation, which leads to crash

ImageMagick is free and open-source software used for editing and manipulating digital images. Prior to versions 7.1.2-15 and 6.9.13-40, a logic error in YUV sampling factor validation allows an invalid sampling factor to bypass checks and trigger a division-by-zero during image loading, resulting in a reliable denial-of-service. Versions 7.1.2-15 and 6.9.13-40 contain a patch.