title: SlickGrid - applying getItemMetadata making the row to loose its id
body: <p>I have the following problem:</p>
  
  <p><a href="http://jsfiddle.net/neoswf/Tvpf5/" rel="nofollow"><strong><em>>>>>>>> Link to a JsFiddle demonstration >>>>>></em></strong></a></p>
  
  <p>I have used the <a href="http://mleibman.github.com/SlickGrid/examples/example5-collapsing.html" rel="nofollow">collapse example</a>, and added getItemMetadata method.</p>
  
  <pre><code>dataView.getItemMetadata = function (row) {
          var thtId = data[row].id;
          if (data[thtId + 1] &amp;&amp; data[thtId + 1].indent &gt; data[thtId].indent) {
              return { 'cssClasses': 'parentClassName' }
          }
      };
  </code></pre>
  
  <p>This works fine until I try to collapse and expanding my rows. Than I get the following error (only on expanding):</p>
  
  <blockquote>
    <p>Uncaught TypeError: Cannot read property 'id' of undefined</p>
  </blockquote>
  
  <p>From my experience, this error accrue when the dataView looses the children's properties. 
  I investigated more and saw that the code fall in the <em>appendRowHtml</em> function (slick.grid.js#1217).</p>
  
  <p>Does anyone has expirience with collapsing feature &amp; getItemMetadata?</p>
  
  <p>Thank You!</p>