ImageMagick's MSL: Stack overflow via infinite recursion in ProcessMSLScript

ImageMagick is free and open-source software used for editing and manipulating digital images. Versions prior to 7.1.2-13 have a stack overflow via infinite recursion in MSL (Magick Scripting Language) `<write>` command when writing to MSL format. Version 7.1.2-13 fixes the issue.