Set coded_frame to NULL when closing a codec, since it might

be invalid after the codec is "gone".

Originally committed as revision 23101 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/utils.c

@@ -709,6 +709,7 @@ av_cold int avcodec_close(AVCodecContext *avctx)
     if (avctx->codec && avctx->codec->close)
         avctx->codec->close(avctx);
     avcodec_default_free_buffers(avctx);
+    avctx->coded_frame = NULL;
     av_freep(&avctx->priv_data);
     if(avctx->codec && avctx->codec->encode)
         av_freep(&avctx->extradata);