do not display an error message if the category of the domain tree does not...

do not display an error message if the category of the domain tree does not exist, so the user can change of base category


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@2501 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Form/ListBox.py

@@ -110,7 +110,7 @@ def makeTreeBody(form, root_dict, domain_path, depth, total_depth, unfolded_list
         domain_path = domain_path[1:]
       else:
         domain_path = ()
-    is_empty_level = (root.objectCount() == 0) and (len(domain_path) != 0)
+    is_empty_level = root is not None and (root.objectCount() == 0) and (len(domain_path) != 0)
     if is_empty_level: base_category = domain_path[0]
 
   tree_body = ''