[Secure-testing-team] Bug#833812: Prevent possible stack overflow

[Bastien ROUCARIES]

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




Prevent possible stack overflow

    Prevent stack overflow by checking if string is null

    (cherry picked from commit 6ea4d4e9eeac1e287bdbfda84f67fb1e50242fb5)

    origin: upstream,
https://github.com/ImageMagick/ImageMagick/commit/6ea4d4e9eeac1e287bdbfda84f67fb1e50242fb5