fix exception

orders/models.py

@@ -64,6 +64,7 @@ class Order(models.Model):
         for p in res:
             pids.append(p['product_id'][0])
             partner_id = p['partner_id'][0]
+        used_coeffs = None
         if len(pids) > 0:
             # Adding barcode and other data for every purchased product
             f = ['barcode', 'product_tmpl_id', 'shelf_id']