Don't return invoices on button method

Replace it by reading commissions on the creation wizard for the opening action.

issue4555
review13981003

commission.py

@@ -320,7 +320,6 @@ class Commission(ModelSQL, ModelView):
         if to_write:
             cls.write(*to_write)
         Invoice.update_taxes(invoices)
-        return invoices
 
     def _group_to_invoice_key(self):
         direction = {
@@ -456,10 +455,11 @@ class CreateInvoice(Wizard):
         Commission = pool.get('commission')
         commissions = Commission.search(self.get_domain(),
             order=[('agent', 'DESC'), ('date', 'DESC')])
-        invoices = Commission.invoice(commissions)
+        Commission.invoice(commissions)
+        invoice_ids = list({c.invoice_line.invoice.id for c in commissions})
         encoder = PYSONEncoder()
         action['pyson_domain'] = encoder.encode(
-            [('id', 'in', [i.id for i in invoices])])
+            [('id', 'in', invoice_ids)])
         action['pyson_search_value'] = encoder.encode([])
         return action, {}