Workfow action dialog should not fail when listbox is empty

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@24654 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Form/Extensions/Folder_getWorkflowActionDocumentList.py

@@ -144,7 +144,11 @@ def getWorkflowActionDocumentList(self, **kw):
   """This returns the list of all documents on which we will pass a workflow
   transition.
   """
-  listbox = kw['listbox']
+  listbox = kw.get('listbox', None)
+  if listbox is None:
+    # if the listbox is empty
+    return []
+
   selection_name = kw['module_selection_name']
   document_list = []
   portal = self.getPortalObject()