[Bug Report] 使用Grid报Maximum call stack size exceeded问题

### VUX version
2.9.2

### OS/Browsers version
MAC/Chrome

### Vue version
2.5.17-beta.0

### Code

```html

import { Grid, GridItem } from 'vux'
export default {
name: "grid",
components: {
Grid,
GridItem
},
methods: {
onItemClick () {
console.log('on item click')
}
}
}

.grid-center {
display: block;
text-align: center;
color: #666;
}
.weui-grids {
background-color: #fff;
}

```

### Steps to reproduce
VUE版本为：2.9.6，使用VUX2的Grid组件时只要使用了就会出现，如果把label="xxxx"换成：:label="$t('Grid')"好像就没事但会报：$t is not defined，我没配置i18n，因为我只想用中文。文档说能直接使用字符label，请问是我哪用错了么？
Uncaught RangeError: Maximum call stack size exceeded
at observe (vue.esm.js?efeb:940)
at initState (vue.esm.js?efeb:3313)
at VueComponent.Vue._init (vue.esm.js?efeb:4628)
at new VueComponent (vue.esm.js?efeb:4798)
at createComponentInstanceForVnode (vue.esm.js?efeb:4310)
at init (vue.esm.js?efeb:4131)
at createComponent (vue.esm.js?efeb:5608)
at createElm (vue.esm.js?efeb:5555)
at createChildren (vue.esm.js?efeb:5682)
at createElm (vue.esm.js?efeb:5584)

### What is Expected?
能在Grid加label

### What is actually happening?
加了就报Maximum call stack size exceeded错误