branches/zip: buf_LRU_block_free_non_file_page(): Flag block->frame

allocated before overwriting some fields and flagging the frame freed.
Some of the buffer frame may have been flagged freed by the user
(such as mem_heap).

buf/buf0lru.c

@@ -1132,6 +1132,7 @@ buf_LRU_block_free_non_file_page(
 
 	buf_block_set_state(block, BUF_BLOCK_NOT_USED);
 
+	UNIV_MEM_ALLOC(block->frame, UNIV_PAGE_SIZE);
 #ifdef UNIV_DEBUG
 	/* Wipe contents of page to reveal possible stale pointers to it */
 	memset(block->frame, '\0', UNIV_PAGE_SIZE);