avformat/id3v2: Fix double-free on error

ff_id3v2_parse_priv_dict() uses av_dict_set() with the flags
AV_DICT_DONT_STRDUP_KEY and AV_DICT_DONT_STRDUP_VAL. In this case both
key and value are freed on error (and owned by the destination
dictionary on success), so that freeing them again on error is a
double-free and therefore forbidden. But it nevertheless happened.

Fixes CID 1452489 and 1452421.
Signed-off-by: NAndreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: NMichael Niedermayer <michael@niedermayer.cc>

libavformat/id3v2.c

@@ -1264,8 +1264,6 @@ int ff_id3v2_parse_priv_dict(AVDictionary **metadata, ID3v2ExtraMeta **extra_met
             }
 
             if ((ret = av_dict_set(metadata, key, escaped, dict_flags)) < 0) {
-                av_free(key);
-                av_free(escaped);
                 return ret;
             }
         }