Add a comment about code assumption which can lead to exceptions.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@19379 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/Document/BusinessTemplate.py

@@ -4557,6 +4557,7 @@ Business Template is a set of definitions, such as skins, portal types and categ
 
       # remove object from old business template
       if len(remove_object_dict):
+        # XXX: this code assumes that there is an installed_bt
         for item_name in installed_bt._item_name_list:
           item = getattr(installed_bt, item_name, None)
           if item is not None: