it is possible to use only one test instead of 2

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@12039 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ZSQLCatalog/SQLCatalog.py

@@ -1915,8 +1915,7 @@ class Catalog(Folder, Persistent, Acquisition.Implicit, ExtensionClass.Base):
           table_index += 1
         where_expression_list.append(related_method(**table_id))
     # Concatenate expressions
-    if kw.get('where_expression',None) is not None:
-      if len(kw['where_expression']) > 0:
+    if kw.get('where_expression',None) not in (None,''):
       where_expression_list.append(kw['where_expression'])
     where_expression = join(where_expression_list, ' AND ')
     select_expression= join(select_expression_list,',')