TypeError: c.getRootNode is not a function

TypeError: c.getRootNode is not a function

主程序：
xtype: 'formgrid',
title:'测试管理列表',
store:zcgl.store.FormGrid,

store层：
Ext.define("zcgl.store.FormGrid",{
        extend:'Ext.data.Store',
        id:'FormGridStore',
        model:'zcgl.model.FormGrid',
        proxy:{
                type:'ajax',
                url:'/zcgl/service/testLoader.php?key=search',
                reader:{
                        type:'json',
                        //root:'topics'
                },
                writer:{
                        type:'json'
                }
        },
        groupField:'bj',//按照什么字段分组
        autoLoad:true
})

model层：
// User类
Ext.define("zcgl.model.FormGrid",{
        extend:"Ext.data.Model",
        fields:[
                {name:'id',type:'int',sortable:true},
                {name:'bj',type:'string',sortable:true},
                {name:'xh',type:'string',sortable:true},
                {name:'xm',type:'string',sortable:true},
                {name:'xb',type:'string',sortable:true},
                {name:'csrq',type:'string',sortable:true},
                {name:'zzmm',type:'string',sortable:true},
                {name:'jg',type:'string',sortable:true},
                {name:'sfzhm',type:'string',sortable:true},
                {name:'mz',type:'string',sortable:true}
        ]
})

可能是js文件没完全加载，可以清空浏览器高速缓存试试
或者你的js框架兼容性有问题，下载最新的版本试试