【ExtJS】错误：this.config[...].width为空或不是对象

var grid = new Ext.grid.GridPanel({
        store: store,
        columns: [
            {id : 'company',header: 'Company', width: 160, sortable: true, dataIndex: 'company'},
            {header: 'Price', width: 75, sortable: true, renderer: 'usMoney', dataIndex: 'price'},
            {header: 'Change', width: 75, sortable: true, renderer: change, dataIndex: 'change'},
            {header: '% Change', width: 75, sortable: true, renderer: pctChange, dataIndex: 'pctChange'},
            {header: 'Last Updated', width: 85, sortable: true, renderer: Ext.util.Format.dateRenderer('m/d/Y'), dataIndex: 'lastChange'}
        ],
        stripeRows: true,
        autoExpandColumn: 'company',
        height: 350,
        width: 600,
        title: 'Array Grid',
        // config options for stateful behavior
        stateful: true,
        stateId: 'grid'       
    });

上面代码中红颜色hightlight的id去掉，刷新页面报：this.config[...].width为空或不是对象的错误。查看Ext API帮助文档，其中Column类中对id的解释中最后一句：
      The Ext.grid.GridPanel.autoExpandColumn grid config option references the column via this unique identifier.
      而GridPanel对autoExpandColumn的解释如下：
      autoExpandColumn : String

      The id of a column in this grid that should expand to fill unused space. This value specified here can not be 0.

      解决该问题的方法是:

     1.恢复操作，即把id : 'company'添加回去。

     2.把autoExpandColumn: 'company',去掉。