Hide DisableDelete warning when creating a new topic

There's no sense in warning that the current topic can't be deleted when it hasn't even yet been created. This is relevant for new topics of protected types, such as containers.

Author: JeremyCaney

OnTopic.Editor.AspNetCore/Areas/Editor/Views/Editor/Edit.cshtml

@@ -20,7 +20,7 @@
   <div id="FormArea" class="row form area">
 
     <div class="col-md-12">
-      @if (Model.ContentTypeDescriptor.DisableDelete) {
+      @if (Model.ContentTypeDescriptor.DisableDelete && !Model.IsNew) {
         <div class="alert alert-warning" role="alert">
           <button type="button" class="close" data-dismiss="alert"><span aria-hidden="true">×</span><span class="sr-only">Close</span></button>
           <strong>Warning:</strong> This topic is part of the OnTopic internal organizational structure and is not intended to be modified. Deletion of this Topic has been disabled.