libavcodec/libmp3lame: Don't free user-provided AVPacket

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavcodec/libmp3lame.c

@@ -279,7 +279,6 @@ static int mp3lame_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
         if ((discard_padding < avctx->frame_size) != (avpkt->duration > 0)) {
             av_log(avctx, AV_LOG_ERROR, "discard padding overflow\n");
             av_packet_unref(avpkt);
-            av_free(avpkt);
             return AVERROR(EINVAL);
         }
         if ((!s->delay_sent && avctx->initial_padding > 0) || discard_padding > 0) {
@@ -288,7 +287,6 @@ static int mp3lame_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
                                                          10);
             if(!side_data) {
                 av_packet_unref(avpkt);
-                av_free(avpkt);
                 return AVERROR(ENOMEM);
             }
             if (!s->delay_sent) {