avformat/mov: disallow a zero sample size in trun atoms

In order to not generate 0 sized packets or create a huge index table
needlessly.

Fixes: Timeout
Fixes: 43717/clusterfuzz-testcase-minimized-ffmpeg_IO_DEMUXER_fuzzer-5206008287330304
Fixes: 45738/clusterfuzz-testcase-minimized-ffmpeg_IO_DEMUXER_fuzzer-6142535657979904

Signed-off-by: Marton Balint <cus@passwd.hu>

libavformat/mov.c

@@ -5179,6 +5179,8 @@ static int mov_read_trun(MOVContext *c, AVIOContext *pb, MOVAtom atom)
         distance++;
         if (av_sat_add64(dts, sample_duration) != dts + (uint64_t)sample_duration)
             return AVERROR_INVALIDDATA;
+        if (!sample_size)
+            return AVERROR_INVALIDDATA;
         dts += sample_duration;
         offset += sample_size;
         sc->data_size += sample_size;