fixed problem with the tag is empty

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@16915 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Type/Core/Folder.py

@@ -456,7 +456,7 @@ class Folder(CopyContainer, CMFBTreeFolder, CMFHBTreeFolder, Base, FolderMixIn,
           id_list[-remaining_id_count:],
           migration_generate_id_method, tag)
     else:
-      tag = ''
+      tag = 'nothing'
     # copy from btree to hbtree
     self.activate(activity="SQLQueue", after_tag=tag)._launchCopyObjectToHBTree(tag)