Flex tree : make caret not appear when tree node has no children

Is there any way to prevent displaying the ">" caret before the tree node if the node has no children? I'd like it to not display when children is an empty ArrayCollection. I know you can set the arraycollection to null but I'd prefer to avoid then having to do all the null checks throughout the code.

create a custom renderer like this:

 package com.simmone.renderers {
  import mx.collections.*;
  import mx.controls.treeClasses.*;
  import mx.controls.listClasses.ListBase;

  public class MyTreeItemRenderer extends TreeItemRenderer {
    public function MyTreeItemRenderer() {
      super();
    }

    override protected function updateDisplayList(unscaledWidth:Number,  
                                                  unscaledHeight:Number):void {
      super.updateDisplayList(unscaledWidth, unscaledHeight);

      if( data.children.length == 0 ) {
        super.disclosureIcon.visible = false;
      }
    }
  }
}

mxml:

 <fx:Script>
    <![CDATA[
      import mx.collections.ArrayCollection;

      private var dataArray:Array = [
        {label:"father1", children:
          [{label:"child1"},
           {label:"child2"}]},
        {label:"father2", children:[]}];

      [Bindable]
      private var dataList:ArrayCollection = new ArrayCollection(dataArray);
    ]]>
  </fx:Script>

 <mx:Tree id="tr1" width="100%" height="80"
          dataProvider="{dataList}"
          labelField="label"
          borderVisible="false"
          itemRenderer="com.simmone.renderers.MyTreeItemRenderer"/>

and I find that if use xmllist, haven't this problem, if no children, will not display discloure icon.