title: AngularJS concat filter issue with ng-repeat
body: <p>I have a filter which concatenates arrays of objects into a single array of objects. It works on objects set up in the controller but is not working in my view.</p>
  
  <p>My filter:</p>
  
  <pre><code>angular.module('hcApp')
  .filter('combine', function() {
    return function(items) {
       return [].concat.apply([],items);
    };
  });
  </code></pre>
  
  <p>Here is an example filter being used successfully:
  Controller:</p>
  
  <pre><code>$scope.obj =[ 
  [{"day":"10","title":"day","summary":"summary","description":"ok","_id":"53f25185bffedb83d8348b22"}],
  [{"day":"3","title":"day","summary":"summary","description":"ok","_id":"53f25185bffedb83d8348b22"}]];
  </code></pre>
  
  <p>View:</p>
  
  <pre><code>&lt;div ng-repeat="event in obj"&gt; 
    &lt;p&gt;{{event}}&lt;/p&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>Executed logic:</p>
  
  <pre><code>[{"day":"3","title":"day","summary":"summary","description":"ok","_id":"53f25185bffedb83d8348b22"}
  {"day":"10","title":"day","summary":"summary","description":"ok","_id":"53f25185bffedb83d8348b22"}]
  </code></pre>
  
  <p>With my actual data I am filtering a complex JSON object with the following code in my view:</p>
  
  <pre><code>&lt;div class="calDynamic" data-ng-repeat="n in [] | range:100"&gt;
  &lt;div ng-repeat="cal in calendar[n].year | filterKey:month"&gt;
   &lt;p&gt;{{cal}}&lt;/p&gt;
  &lt;div ng-repeat="items in cal "&gt;    
          &lt;a href="/events/{{items.day}}"&gt;
            &lt;article class="eventslist"&gt;
             &lt;div class="numberedDate"&gt;
                 &lt;h3&gt;{{items.day}}&lt;/h3&gt;
              &lt;/div&gt;
              &lt;div class="calInfo"&gt;
                &lt;h5&gt;{{items.title}}&lt;/h5&gt;
                 &lt;p&gt;{{items.summary}}&amp;nbsp;&lt;a&gt;more&lt;/a&gt;&lt;/p&gt;
              &lt;/div&gt;
             &lt;/article&gt;                
        &lt;/div&gt;
  &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>{{cal}} is returning data formatted the same as the data in the $scope.obj but when I add the filter:</p>
  
  <pre><code>&lt;div ng-repeat="cal in calendar[n].year | filterKey:month | combine"&gt;
  </code></pre>
  
  <p>{{cal}} returns blank instead of returning the restructured array. Is there a problem with my set up or filter? It seems like it should work.</p>