list.jsを使ってテーブルをソートしたらテーブルの中身が全部消えます。何故でしょうか...

<!DOCTYPE html>
<html lang="ja">
<head>
<meta charset="utf-8">
   <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
   <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"></script>
   <script src="../scripts/script.js"></script>
<body>
   <div id='itemlist'>

      <button class='sort desc' data-sort='date'>Sort By Date</button>

      <table>
         <tbody class='list'>

         </tbody>
      </table>
   </div>

   <script src="//cdnjs.cloudflare.com/ajax/libs/list.js/1.5.0/list.min.js"></script>
   <script type='text/javascript'>
      var options = {
      // 検索するターゲットデータ
      valueNames: [ 'date', 'elem' ]
      };

   // ターゲットとなるID
      var itemList = new List('itemlist', options);
   </script>
</body>
</html>

$(function() {

  var url = ["all-c_int.xml","all-dom.xml"];
  var feed = new Object();

  $.each(url, function(index, value){

    $.ajax({
      url: value,
      type:"GET",
      dataType:"xml",
      timeout:1000,
      xhrFields: {
        withCredentials: true
      },
      cache: false,
        error:function(){
          alert("Failed to load XML");
        },
        success:function(xml){
          $(xml).find("item").each(function(){
            var item_link=$(this).find("link").text();
            var item_title=$(this).find("title").text();
            var item_desc=$(this).find("description").text();
            var item_date=dateParse($(this).find('pubDate').text());
            feed[item_date] = "<tr><td class='date'>"+item_date+"</td><td class='elem'><a href='"+item_link+"'>"+item_title+"</a>"+item_desc+"</td></tr>";
            if(item_title!="") $(feed[item_date]).appendTo("tbody");

          });
        }
      });

  });

    function dateParse(str){
      var dateObject = new Date(str);
      year = dateObject.getFullYear();
      month = dateObject.getMonth();
      day = dateObject.getDate();
      hour = dateObject.getHours();
      minute = dateObject.getMinutes();
      second = dateObject.getSeconds();

      if (month < 10) { month ="0" + month; }
      if (day < 10) { day = "0" + day; }
      if (hour < 10) { hout = "0" + hour; }
      if (minute < 10) { minute = "0" + minute; }
      if (second < 10) { second = "0" + second; }

      return year + "/" + month + "/" + day + " " + hour + ":" + minute + ":" + second + " ";
    }

});