avformat/mov: Check extradata in mov_read_iacb()

Fixes: MemLeak
Fixes: 69853/clusterfuzz-testcase-minimized-ffmpeg_dem_MOV_fuzzer-4660448545275904

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/mov.c

@@ -898,6 +898,11 @@ static int mov_read_iacb(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     st = c->fc->streams[c->fc->nb_streams - 1];
     sc = st->priv_data;
 
+    if (st->codecpar->extradata) {
+        av_log(c->fc, AV_LOG_WARNING, "ignoring iacb\n");
+        return 0;
+    }
+
     sc->iamf = av_mallocz(sizeof(*sc->iamf));
     if (!sc->iamf)
         return AVERROR(ENOMEM);