fix #1156 add defensive coding for scenario where host name does not match any alias

Oqtane.Server/Pages/_Host.cshtml

@@ -1,4 +1,4 @@
-@page "/"
+@page "/"
 @namespace Oqtane.Pages
 @addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
 @using Microsoft.Extensions.Configuration
@@ -35,6 +35,11 @@
         <a class="dismiss">🗙</a>
     </div>
 
+    @if (Model.Message != "")
+    {
+        @Model.Message
+    }
+
     <script src="js/interop.js"></script>
 
     @if (Configuration.GetSection("Runtime").Value == "WebAssembly")