avformat/mxfdec: Fix memleak when adding element to array fails

Said array contains pointers to other structs and both the designated
new element as well as other stuff contained in it (e.g. strings) leak
if the new element can't be added to the array.

Reviewed-by: Tomas Härdin <tjoppen@acc.umu.se>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
(cherry picked from commit 49e78548c3)

libavformat/mxfdec.c

@@ -821,15 +821,17 @@ static int mxf_read_partition_pack(void *arg, AVIOContext *pb, int tag, int size
     return 0;
 }
 
-static int mxf_add_metadata_set(MXFContext *mxf, void *metadata_set)
+static int mxf_add_metadata_set(MXFContext *mxf, MXFMetadataSet **metadata_set)
 {
     MXFMetadataSet **tmp;
 
     tmp = av_realloc_array(mxf->metadata_sets, mxf->metadata_sets_count + 1, sizeof(*mxf->metadata_sets));
-    if (!tmp)
+    if (!tmp) {
+        mxf_free_metadataset(metadata_set, 1);
         return AVERROR(ENOMEM);
+    }
     mxf->metadata_sets = tmp;
-    mxf->metadata_sets[mxf->metadata_sets_count] = metadata_set;
+    mxf->metadata_sets[mxf->metadata_sets_count] = *metadata_set;
     mxf->metadata_sets_count++;
     return 0;
 }
@@ -2782,7 +2784,7 @@ static int mxf_read_local_tags(MXFContext *mxf, KLVPacket *klv, MXFMetadataReadF
             avio_seek(pb, next, SEEK_SET);
     }
     if (ctx_size) ctx->type = type;
-    return ctx_size ? mxf_add_metadata_set(mxf, ctx) : 0;
+    return ctx_size ? mxf_add_metadata_set(mxf, &ctx) : 0;
 }
 
 /**
@@ -3085,10 +3087,8 @@ static int mxf_handle_missing_index_segment(MXFContext *mxf, AVStream *st)
     if (!(segment = av_mallocz(sizeof(*segment))))
         return AVERROR(ENOMEM);
 
-    if ((ret = mxf_add_metadata_set(mxf, segment))) {
-        mxf_free_metadataset((MXFMetadataSet**)&segment, 1);
+    if ((ret = mxf_add_metadata_set(mxf, (MXFMetadataSet**)&segment)))
         return ret;
-    }
 
     /* Make sure we have nonzero unique index_sid, body_sid will be ok, because
      * using the same SID for index is forbidden in MXF. */