slapos_accounting: ensure trade condition is found

master/bt5/slapos_accounting/SkinTemplateItem/portal_skins/slapos_accounting/InstanceTree_requestUpdateOpenSaleOrder.py

@@ -124,6 +124,10 @@ if instance_tree.getCausalityState() == 'diverged':
 
       predicate_list = []
       inherited_trade_condition = open_sale_order.getSpecialiseValue()
+
+      if specialise is None:
+        assert inherited_trade_condition is not None
+
       while inherited_trade_condition is not None:
         predicate_list.extend([
           x for x in inherited_trade_condition.contentValues(portal_type='Sale Supply Line')