slapos_accounting: set the source payment before finalising the sale invoice

master/bt5/slapos_accounting/SkinTemplateItem/portal_skins/slapos_simulation/SaleInvoiceTransaction_postSlapOSSaleInvoiceTransactionLineGeneration.py

@@ -3,5 +3,8 @@ from Products.ERP5Type.Message import translateString
 comment = translateString('Initialised by Delivery Builder.')
 isTransitionPossible = context.getPortalObject().portal_workflow.isTransitionPossible
 
+if context.getSourcePayment("") == "":
+  context.setSourcePayment(context.AccountingTransaction_getSourcePaymentItemList()[-1][1])
+
 if isTransitionPossible(context, 'startBuilding'):
   context.startBuilding(comment=comment)