avformat/ipmovie: Check OPCODE_CREATE_TIMER size

Fixes use of uninitialized memory
Fixes: msan_uninit-mem_7f81e836ef8c_5930_ipmovie_interplayvideo_interplay_dpcm__bislogo.mve
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/ipmovie.c

@@ -321,7 +321,7 @@ static int process_ipmovie_chunk(IPMVEContext *s, AVIOContext *pb,
 
         case OPCODE_CREATE_TIMER:
             av_dlog(NULL, "create timer\n");
-            if ((opcode_version > 0) || (opcode_size > 6)) {
+            if ((opcode_version > 0) || (opcode_size != 6)) {
                 av_dlog(NULL, "bad create_timer opcode\n");
                 chunk_type = CHUNK_BAD;
                 break;