title: dhtmlxTree scrolling issue
body: <p>I face a little issue with dhtmlxTree: nodes are not loading if I try scrolling the tree at a considerable speed with smart rendering on. My code (without data) is the next:</p>
  
  <pre><code>myTree = new dhtmlXTreeObject("treeboxbox_tree", "100%", "100%", 0);
  myTree.setImagePath("…/images/");
  myTree.setXMLAutoLoading("php/json.php");
  //myTree.setXMLAutoLoading("…/php/json.php");
  myTree.setDataMode("json");
  myTree.enableSmartRendering(true);
  //load first level of tree
  myTree.loadJSON("php/json.php?id=0");
  </code></pre>