Receipt page fixes (#6079)

* Receipt: Don't assign empty values to data; hide present empty values
* Receipt: Use same URL on "Return to Store" link as on invoice

BTCPayServer/Models/InvoicingModels/InvoiceReceiptViewModel.cs

@@ -20,6 +20,6 @@ namespace BTCPayServer.Models.InvoicingModels
         public Dictionary<string, object> CartData { get; set; }
         public ReceiptOptions ReceiptOptions { get; set; }
         public List<ViewPaymentRequestViewModel.PaymentRequestInvoicePayment> Payments { get; set; }
-        public string OrderUrl { get; set; }
+        public string RedirectUrl { get; set; }
     }
 }