title: ODataActionFilter being called twice
body: <p>This is my first attempt at using breeze.js so I probably have something setup incorrectly, but not sure what it is.</p>
  
  <p>I am experiencing an error when executing a simple query.  I'm using EF 5.0 DB first in a VS2012 project.</p>
  
  <p>An error has occurred.
  Value cannot be null. Parameter name: source
  System.ArgumentNullException
  
  at System.Linq.Queryable.Where[TSource](IQueryable<code>1 source, Expression</code>1 predicate) at lambda_method(Closure , IQueryable ) at Breeze.WebApi.ODataActionFilter.OnActionExecuted(HttpActionExecutedContext actionExecutedContext) at System.Web.Http.Filters.ActionFilterAttribute.CallOnActionExecuted(HttpActionContext actionContext, HttpResponseMessage response, Exception exception) at System.Web.Http.Filters.ActionFilterAttribute.&lt;>c_<em>DisplayClass2.b</em>_0(HttpResponseMessage response) at System.Threading.Tasks.TaskHelpersExtensions.&lt;>c__DisplayClass41<code>2.&lt;Then&gt;b__40(Task</code>1 t) at System.Threading.Tasks.TaskHelpersExtensions.ThenImpl[TTask,TOuterResult](TTask task, Func`2 continuation, CancellationToken cancellationToken, Boolean runSynchronously)
  
  </p>
  
  <p>In an attempt to determine what I was doing incorrectly, I download the breeze server source code  and included the project in the solution so I could trace the error.  The error is occurring in the OnActionExecuted event in ODataActionFilter.cs.  The strange thing is that the function is called twice for the same query.  The function is first called with the query in the responseObject.  The 2nd time the event is called, the result of the query is in the responseObject.  This is no longer a iQueryable object which results in the error.  I cannot determine why the function is being called a 2nd time when it already has the correct result.</p>
  
  <p>Has anyone seen this before and can tell point me in a direction to fix it?</p>
  
  <p>thanks</p>