GHSA-X928-4434-CRQJ ImageMagick has a memory leak in PNG encoder when writing a MNG image

When the PNG encoder fails to write an MNG image it can leak memory...

UBUNTU-CVE-2017-13139

In ImageMagick before 6.9.9-0 and 7.x before 7.0.6-1, the ReadOneMNGImage function in coders/png.c has an out-of-bounds read with the MNG CLIP chunk...