[Bug Report] v-chart的repaint方法提示错误

### VUX version
2.9.2

### OS/Browsers version
Chrome

### Vue version
2.5.17-beta.0

### Code

```html
new Promise((resolve,reject) => {
//伪代码，表明是在Promise中数据修改，需要清楚重新渲染（仅重新渲染在手机端滑动的时候会闪动显示旧数据）
if (this.$refs.vChartView) {
console.log('renderVChart', this.$refs.vChartView);
this.$refs.vChartView.repaint();
}
})

```

### Steps to reproduce
vChart数据修改后，调用repaint()方法。

### What is Expected?
图表清除并重新渲染。

### What is actually happening?
控制台输出
renderVChart VueComponent {_uid: 21, _isVue: true, $options: {…}, _renderProxy: Proxy, _self: VueComponent, …}

Uncaught (in promise) TypeError: Cannot read property 'repaint' of undefined

报错，提示 Uncaught (in promise) TypeError: Cannot read property 'repaint' of undefined