avformat/dfa: Fix packet leak on error

Fixes: 07fa81f300736485e585b63e7b1cd155/signal_sigabrt_7ffff6ae7cb7_16_94ee815791a1357826524072db5bc2dc.dfa

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/dfa.c

@@ -101,6 +101,7 @@ static int dfa_read_packet(AVFormatContext *s, AVPacket *pkt)
         frame_size = AV_RL32(pkt->data + pkt->size - 8);
         if (frame_size > INT_MAX - 4) {
             av_log(s, AV_LOG_ERROR, "Too large chunk size: %"PRIu32"\n", frame_size);
+            av_packet_unref(pkt);
             return AVERROR(EIO);
         }
         if (AV_RL32(pkt->data + pkt->size - 12) == MKTAG('E', 'O', 'F', 'R')) {