qx.Classes members problem. [fixed]

<!DOCTYPE HTML>
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>qx.Classes Test</title>
    <script type="text/javascript" src="http://demo.qooxdoo.org/2.1/framework/qx-oo-2.1.min.js"></script>
</head>
<body style="background-color: rgb(219,230,253);">
    <div id="test">
    </div>
    <script type="text/javascript">
        qx.Class.define("com.BaseClass",
        {
            extend : qx.core.Object,

        construct: function() {
              this._children = [];
            },

            members:
            {
                _children: null,

                getChildrenCount: function(){
                    return this._children.length;
                },

                addChild: function(child){
                    this._children.push(child);
                }
            }
        });

        var class1 = new com.BaseClass();
        var class2 = new com.BaseClass();
        console.log("class1.getChildrenCount() - " + class1.getChildrenCount())
        console.log("class2.getChildrenCount() - " + class2.getChildrenCount())
        class1.addChild("somechild");
        console.log("class1.getChildrenCount() - " + class1.getChildrenCount())
        console.log("class2.getChildrenCount() - " + class2.getChildrenCount())
    </script>
</body>
</html>