[Secure-testing-team] Bug#832475: Fix a outofbound access for psd file

[Bastien ROUCARIES]

Package: imagemagick
Version: 8:6.7.7.10-5
Severity: grave
Tags: patch security
X-Debbugs-CC: secure-testing-team at lists.alioth.debian.org

Split of 823750
    Fix a outofbound access for psd file

    Added extra check to fix
https://github.com/ImageMagick/ImageMagick/issues/93

    origin: upstream,
https://github.com/ImageMagick/ImageMagick/commit/4b1b9c0522628887195bad3a6723f7000b0c9a58
    bug: https://github.com/ImageMagick/ImageMagick/issues/93
    bug-ubuntu:
https://bugs.launchpad.net/ubuntu/+source/imagemagick/+bug/1537419