Just revert the commit r27857.

The reason why:
For example, if a parameter is set a None in the 'Default Parameters'
property in a Listbox configuration, the parameter unfortunately discarded.


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@27868 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Form/ListBox.py

@@ -100,7 +100,7 @@ class CatalogMethodWrapper(MethodWrapper):
     # It is probably needed at a more generic level (Forms ? Selection ?), or
     # even a more specific one (limited to HTML ?)...
     for key, value in kw.items():
-      if value == '' or value is None:
+      if value == '':
         kw.pop(key)
     return getattr(self.context, self.method_name)(*args, **kw)