avcodec/codec_par: always free side data in the destination AVCodecContext

Signed-off-by: James Almer <jamrial@gmail.com>

libavcodec/codec_par.c

@@ -253,8 +253,8 @@ FF_ENABLE_DEPRECATION_WARNINGS
         break;
     }
 
-    if (par->extradata) {
     av_freep(&codec->extradata);
+    if (par->extradata) {
         codec->extradata = av_mallocz(par->extradata_size + AV_INPUT_BUFFER_PADDING_SIZE);
         if (!codec->extradata)
             return AVERROR(ENOMEM);