erp5_decision: Do not crash when source decision is not indicated in business process

bt5/erp5_decision/SkinTemplateItem/portal_skins/erp5_decision/Decision_afterGeneration.py

@@ -12,7 +12,10 @@ if isTransitionPossible(decision, 'post'):
 
   # set some meaningful title
   action_type = 'Approval'
-  title = '%s by %s' %(action_type, source_decision_value.getTitle())
-  decision.setTitle(title)
+  if source_decision_value is None:
+    decision.setTitle(action_type)
+  else:
+    title = '%s by %s' %(action_type, source_decision_value.getTitle())
+    decision.setTitle(title)
 
   decision.post()