如何摆脱extjs树中的图标

.x-tree-icon {
    display: none;
}

var node = Ext.getCmp('myTree').getRootNode().firstChild;
node.set('iconCls', '');

var store = Ext.create('Ext.data.TreeStore', {
    root: {
        expanded: true,
        children: [
            { text: "Node 1", leaf: true },
            { text: "Node 2", leaf: true }
        ]
    }
});

var tree = Ext.create('Ext.tree.Panel', {
    store: store,
    rootVisible: false,
    renderTo: Ext.getBody(),
    displayField: 'text',
    columns: [
        {
            xtype: 'treecolumn',
            text: 'Name',
            flex: 1,
            dataIndex: 'text',
            renderer: function(value, record) {
                return value;
            }
        }
    ]
});