catch an exception if specialise is None.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@33115 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/Document/TradeModelLine.py

@@ -190,8 +190,11 @@ class TradeModelLine(Predicate, XMLMatrix, Amount):
         # if parent don't have findSpecialiseValueList, this mean it's on the
         # specialise_value
         document = self.getParentValue().getSpecialiseValue()
+      try:
         business_process_list = document.findSpecialiseValueList(
             context=context, portal_type_list=['Business Process'])
+      except AttributeError:
+        business_process_list = []
       business_process = None
       property_dict = {}
       if len(business_process_list):