fix building by BCC without NGX_DEBUG_MALLOC
diff --git a/src/core/ngx_slab.c b/src/core/ngx_slab.c
index cca8374..870c59b 100644
--- a/src/core/ngx_slab.c
+++ b/src/core/ngx_slab.c
@@ -584,9 +584,9 @@
 
         ngx_slab_free_pages(pool, &pool->pages[n], size);
 
-        size <<= ngx_pagesize_shift;
+        ngx_slab_junk(p, size << ngx_pagesize_shift);
 
-        goto done;
+        return;
     }
 
     /* not reached */