SupplyBindingModel fix

ComputerShopProvider/ComputerShopContracts/BindingModels/SupplyBindingModel.cs

@@ -13,7 +13,7 @@ namespace ComputerShopContracts.BindingModels
         public int Id { get; set; }
         public int ClientId { get; set; }
 
-        public int ReceivingId { get; set; }
+        public int? ReceivingId { get; set; }
         public SupplyStatus Status { get; set; } = SupplyStatus.Неизвестен;
 
         public DateTime DateCreate { get; set; } = DateTime.Now;