avformat/matroskaenc: Fix potential leak of cached packet

If mkv_write_trailer() is not called, the cached audio packet might
leak; so unref it in mkv_deinit().
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/matroskaenc.c

@@ -390,6 +390,8 @@ static void mkv_deinit(AVFormatContext *s)
 {
     MatroskaMuxContext *mkv = s->priv_data;
 
+    av_packet_unref(&mkv->cur_audio_pkt);
+
     ffio_free_dyn_buf(&mkv->cluster_bc);
     ffio_free_dyn_buf(&mkv->info_bc);
     ffio_free_dyn_buf(&mkv->tracks_bc);
@@ -2534,7 +2536,6 @@ static int mkv_write_trailer(AVFormatContext *s)
     // check if we have an audio packet cached
     if (mkv->cur_audio_pkt.size > 0) {
         ret = mkv_write_packet_internal(s, &mkv->cur_audio_pkt, 0);
-        av_packet_unref(&mkv->cur_audio_pkt);
         if (ret < 0) {
             av_log(s, AV_LOG_ERROR,
                    "Could not write cached audio packet ret:%d\n", ret);