fixed conflit

app/models/sale.rb

@@ -135,7 +135,13 @@ class Sale < ApplicationRecord
       # shift with terminal zone
 
       # set cashier
-      if order_source.downcase == "emenu"
+      if !order_source.nil?
+        orderSoure = order_source.downcase
+      else
+        orderSoure = nil
+      end
+
+      if orderSoure == "emenu"
         if !booking.dining_facility_id.nil?
           table = DiningFacility.find(booking.dining_facility_id)
           cashier_zone = CashierTerminalByZone.find_by_zone_id(table.zone_id)