default payment term to 0 to avoid error when adding to a datetime object

git-svn-id: https://svn.erp5.org/repos/public/erp5/sandbox/amount_generator@37408 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/Document/BusinessProcess.py

@@ -191,7 +191,7 @@ class BusinessProcess(Path, XMLObject):
     reference_date = explanation_cache.getReferenceDate(self, trade_date, reference_date_method_id)
 
     # Computer start_date and stop_date (XXX-JPS this could be cached and accelerated)
-    start_date = reference_date + trade_model_path.getPaymentTerm() # XXX-JPS Until better naming
+    start_date = reference_date + trade_model_path.getPaymentTerm(0) # XXX-JPS Until better naming
     if delay_mode == 'min':
       delay = trade_model_path.getMinDelay()
     elif delay_mode == 'max':