Fix codegen hidden bugs

codegen/dbl_list/snippets/list_push_back

@@ -1,4 +1,4 @@
-  if (!list || !node || !(node->string)) {{
+  if (!list || !node || !(node->item)) {{
     return;
   }}
 
@@ -9,7 +9,6 @@
     return;
   }}
 
-  list->total_size += node_list.total_size;
   list->node_count += node_list.node_count;
 
   {T}Node *last = list->last;