title: Adding htmlattributes to DropDownList helper changes behaviour
body: <p>Prior to MVC 5 the DropDownList was scaffolded in my Razor Edit View as:</p>
  
  <p><code>@Html.DropDownList("EntityId", String.Empty)</code> </p>
  
  <p>But now the equivalent (post MVC 5) is scaffolded as:</p>
  
  <p><code>@Html.DropDownList("EntityId", null, htmlAttributes: new { @class = "form-control" })</code></p>
  
  <p>I want to add the <code>htmlAttributes</code> to keep the UI consistent, but the DropDownList no longer works as expected for a nullable EntityId <code>(int ? EntityId)</code>. The problem is that the default item is set to the first item in the list if EntityId is null. I want a blank item if the id is null, and the appropriate selection if not.  </p>
  
  <p>PS. My controller builds the list as follows: 
  <code>ViewBag.EntityId = new SelectList(db.Entities, "EntityId", "Name", EntityId);</code></p>