fix 空指针

netflix-service/src/main/java/com/cyksj/service/exchange/impl/ExchangeCodeServiceImpl.java

@@ -145,7 +145,7 @@ public class ExchangeCodeServiceImpl extends ServiceImpl<ExchangeCodeMapper, Exc
 				.eq(OrderDon::getExCode, exchangeCode.getCode())
 				.notIn(OrderDon::getStatus, StatisticsDataScheduler.noOrderStatus)
 				.last("limit 1"));
-		if (orderDon.getStatus() == OrderDon.Status.refund) {
+		if (orderDon != null && orderDon.getStatus() == OrderDon.Status.refund) {
 			throw BusinessRuntimeException.getInstance("您的订单已退款,无法使用该兑换码");
 		}
 		//生成车票订单