avformat/avs: Check if return code is representable

Fixes: leak
Fixes: 62164/clusterfuzz-testcase-minimized-ffmpeg_dem_AVS_fuzzer-6738814988320768

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

libavformat/avs.c

@@ -140,6 +140,10 @@ static int avs_read_audio_packet(AVFormatContext * s, AVPacket * pkt)
         return 0;    /* this indicate EOS */
     if (ret < 0)
         return ret;
+    if (size != (int)size) {
+        av_packet_unref(pkt);
+        return AVERROR(EDOM);
+    }
 
     pkt->stream_index = avs->st_audio->index;
     pkt->flags |= AV_PKT_FLAG_KEY;