avformat/mxfdec: Fix memleak of primer_packs

Fixes: asan_static-oob_87d116_10_201.mxf
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/mxfdec.c

@@ -426,6 +426,10 @@ static int mxf_read_primer_pack(void *arg, AVIOContext *pb, int tag, int size, U
         av_log(mxf->fc, AV_LOG_ERROR, "item_num %d is too large\n", item_num);
         return AVERROR_INVALIDDATA;
     }
+    if (mxf->local_tags)
+        av_log(mxf->fc, AV_LOG_VERBOSE, "Multiple primer packs\n");
+    av_free(mxf->local_tags);
+    mxf->local_tags_count = 0;
     mxf->local_tags = av_calloc(item_num, item_len);
     if (!mxf->local_tags)
         return AVERROR(ENOMEM);