oldgnu_store_sparse_info (struct tar_sparse_file *file, size_t *pindex,
			  struct sparse *sp, size_t sparse_size)
{
  for (; *pindex < file->stat_info->sparse_map_avail
	 && sparse_size > 0; sparse_size--, sp++, ++*pindex)
    {
      OFF_TO_CHARS (file->stat_info->sparse_map[*pindex].offset,
		    sp->offset);
      OFF_TO_CHARS (file->stat_info->sparse_map[*pindex].numbytes,
		    sp->numbytes);
    }
}

The product dereferences a pointer that it expects to be valid but is NULL.