freelist_memalign: fix the address of the previous memory block

src/freelist/memalign.c

@@ -77,7 +77,7 @@ check_alignment:
             size_t previous_size = previous_size_availability >> 1;
             size_t previous_availability = previous_size_availability & 1;
             block_header_t *previous_block = (block_header_t *)
-                ((uintptr_t) block_header - previous_size);
+                ((uintptr_t) block_header - previous_size - HEADER_SIZE);
 
             block_header_t *next_block = get_dlnext(raw_block,
                     block_header);