Fixed half of warnings having to do with allowing Null string objects. (#791)

src/Web/ViewModels/OrderViewModel.cs

@@ -12,6 +12,6 @@ public class OrderViewModel
     public DateTimeOffset OrderDate { get; set; }
     public decimal Total { get; set; }
     public string Status => DEFAULT_STATUS;
-    public Address ShippingAddress { get; set; }
+    public Address? ShippingAddress { get; set; }
     public List<OrderItemViewModel> OrderItems { get; set; } = new List<OrderItemViewModel>();
 }