Debian: CVE-2020-27750: imagemagick -- security update

A flaw was found in ImageMagick in MagickCore/colorspace-private.h and MagickCore/quantum.h. An attacker who submits a crafted file that is processed by ImageMagick could trigger undefined behavior in the form of values outside the range of type `unsigned char` and math division by zero. This would most likely lead to an impact to application availability, but could potentially cause other problems related to undefined behavior. This flaw affects ImageMagick versions prior to 7.0.8-68.