Merge commit 'c3e58f8f'

* commit 'c3e58f8f':
  matroskaenc: restore compatibility with non referenced AVPacket
Merged-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/matroskaenc.c

@@ -1418,8 +1418,11 @@ static int mkv_write_packet(AVFormatContext *s, AVPacket *pkt)
     // keyframe's timecode is contained in the same cluster for WebM
     if (codec->codec_type == AVMEDIA_TYPE_AUDIO) {
         mkv->cur_audio_pkt = *pkt;
+        if (pkt->buf) {
             mkv->cur_audio_pkt.buf = av_buffer_ref(pkt->buf);
             ret = mkv->cur_audio_pkt.buf ? 0 : AVERROR(ENOMEM);
+        } else
+            ret = av_dup_packet(&mkv->cur_audio_pkt);
     } else
         ret = mkv_write_packet_internal(s, pkt);
     return ret;