CGA-mhc8-ggcq-xmpx

The ImageMagic6 project contains the same fix in the same function by the same author as ImageMagic. This can be seen here in ImageMagic6: https://github.com/ImageMagick/ImageMagick6/commit/dfa1270146d8c6f9b252a66228ca15ee62aa75f2 and ImageMagic: https://github.com/ImageMagick/ImageMagick/commit/bac413a26073923d3ffb258adaab07fb3fe8fdc9