avcodec/parser: use av_freep() to avoid leaving stale pointers in memory

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/parser.c

@@ -212,7 +212,7 @@ void av_parser_close(AVCodecParserContext *s)
     if (s) {
         if (s->parser->parser_close)
             s->parser->parser_close(s);
-        av_free(s->priv_data);
+        av_freep(&s->priv_data);
         av_free(s);
     }
 }