CVE-2020-27755: Missing Release of Memory after Effective Lifetime

in SetImageExtent() of /MagickCore/image.c, an incorrect image depth size can cause a memory leak because the code which checks for the proper image depth size does not reset the size in the event there is an invalid size. The patch resets the depth to a proper size before throwing an exception. The memory leak can be triggered by a crafted input file that is processed by ImageMagick and could cause an impact to application reliability, such as denial of service. This flaw affects ImageMagick versions prior to 7.0.9-0.