gst-ffmpeg: fix for Security Advisory CVE-2013-0868
libavcodec/huffyuvdec.c in FFmpeg before 1.1.2 allows remote attackers
to have an unspecified impact via crafted Huffyuv data, related to an
out-of-bounds write and (1) unchecked return codes from the init_vlc
function and (2) len==0 cases.
