修复关联订单bug

BBWYB.Server.Business/PurchaseOrder/PurchaseOrderBusiness.cs

@@ -753,13 +753,14 @@ namespace BBWYB.Server.Business
                 }
             }
 
-            if (dbOrderCost == null)
+            var dbOrderCostIsEmpty = dbOrderCost == null;
+            if (dbOrderCostIsEmpty)
             {
                 dbOrderCost = new OrderCost()
                 {
                     OrderId = request.OrderId,
                     IsManualEdited = false,
-                    CreateTime = DateTime.Now,
+                    CreateTime = DateTime.Now
                 };
             }
 
@@ -772,7 +773,7 @@ namespace BBWYB.Server.Business
                                                           totalOutPackAmount ?? 0M,
                                                           0M);
 
-            if (dbOrderCost == null)
+            if (dbOrderCostIsEmpty)
                 insertOrderCost = fsql.Insert(dbOrderCost);
             else
                 updateOrderCost = fsql.Update<OrderCost>().SetSource(dbOrderCost);