Avoid a NULL pointer dereference in ps file handling. CVE assignment: http://seclists.org/oss-sec/2016/q2/459 Upstream patch: https://anonscm.debian.org/cgit/collab-maint/imagemagick.git/commit/?h=debian-patches/6.8.9.9-4-for-upstream&id=f093a3119704fd6d349a9ee32b9f71cabe7d04c8