vc1dec: add missing terminating element to mpeg4_video_profiles

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/mpeg4videodec.c

@@ -2292,6 +2292,7 @@ static const AVProfile mpeg4_video_profiles[] = {
     { FF_PROFILE_MPEG4_ADVANCED_SCALABLE_TEXTURE, "Advanced Scalable Texture Profile" },
     { FF_PROFILE_MPEG4_SIMPLE_STUDIO,             "Simple Studio Profile" },
     { FF_PROFILE_MPEG4_ADVANCED_SIMPLE,           "Advanced Simple Profile" },
+    { FF_PROFILE_UNKNOWN },
 };
 
 static const AVOption mpeg4_options[] = {