avformat/thp: Check compcount

Fixes: out of array access
Fixes: 22520/clusterfuzz-testcase-minimized-ffmpeg_DEMUXER_fuzzer-5100297658826752

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

libavformat/thp.c

@@ -93,6 +93,9 @@ static int thp_read_header(AVFormatContext *s)
     avio_seek (pb, thp->compoff, SEEK_SET);
     thp->compcount       = avio_rb32(pb);
 
+    if (thp->compcount > FF_ARRAY_ELEMS(thp->components))
+        return AVERROR_INVALIDDATA;
+
     /* Read the list of component types.  */
     avio_read(pb, thp->components, 16);