[Bug Report] 代码错误提示定位错误

### vux-loader version
1.2.9

### OS/Browsers version
window10/chrome v71.0.3578.98

### Vue version
2.5.20

### Code

```html
编写错误代码即可
```

### Steps to reproduce
1.使用vux-loader按需加载组件
2.在created函数中书写错误代码如let obj = {} obj.push()
3.在浏览器中查看错误提示，提示行数不准确
4.在webpack中去掉vux-loader，错误提示正常；

### What is Expected?
代码错误提示定位准确

### What is actually happening?
代码错误提示定位错误