jQuery.ui.widget memory leak

HTML

<script src="https://raw.github.com/jquery/jquery-ui/master/ui/jquery.ui.core.js"></script>
<script src="https://raw.github.com/jquery/jquery-ui/master/ui/jquery.ui.widget.js"></script>
<div id="container">loading...</div>
<div id="console"></div>

JavaScript

// test code
(function($,undefined){
  var count = 0;
  $.widget("ui.dummy",{
    _destroy: function(){
      $("#console").text("call destroy:"+count++);
//      $.Widget.prototype.destroy.call( this );
    }
  });
})(jQuery);
setInterval(function(){
  $("#container")
      .empty()
      .append("<div class='dummy'>dummy</div>")
      .find(".dummy")
          .dummy()
      .end();
},1000);