title: jQuery UI autocomplete missing _renderItem
body: <p>This is weird.</p>
  
  <pre><code>$.fn.autoList = function () {
  
  return this.each(function () {
  
      var self = this;
  
      // initiate autocomplete
      $(self).autocomplete({
          source: _li_data,
          minLength: 2,
          select: function (event, ui) {
              ui.item.checkbox.prop('checked', true).trigger('change');
              ui.item.checked = !ui.item.checked;
              $(event.target).val('');
              return false;
          }
      })
      .data('autocomplete')._renderItem = function (ul, item) {
                      if (item.checked) {
                          return $("&lt;li&gt;")
                                  .text(item.label)
                                  .addClass('preselected')
                                  .appendTo(ul);
                      }
              };
  
  });}
  </code></pre>
  
  <p>When typing and just before the results should render, I get the following error. <code>Uncaught TypeError: Cannot read property 'data' of undefined</code> in jquery-ui-1.9.0.js:6672 which has the following code</p>
  
  <pre><code>    _renderItemData: function( ul, item ) {
      return this._renderItem( ul, item ).data( "ui-autocomplete-item", item );
  },
  </code></pre>
  
  <p>What I want to do is to add a "preselected" class to a -li- item in the -ul- of the autocomplete dropdown. I am stuck with this...</p>