ERROR: /static/js/bundle.js response.ok() is false

### Description

error，response.ok() false
http://localhost:3000/static/js/bundle.js false

### Plugin configration

for example:

```javascript
new SkeletonPlugin({
pathname: path.resolve(__dirname, './shell'), // the path to store shell file
staticDir: path.resolve(__dirname, './build'), // the same as the `output.path`
routes: ['/index', '/user', '/tool' ], // Which routes you want to generate skeleton screen
}),
```

### Versions

- Page Skeleton: v0.10.12
- Webpack: v3.8.1

Reproduce the report with Page Skeleton v0.10.12, Webpack v3.8.1, and the shown SkeletonPlugin configuration, then inspect why /static/js/bundle.js returns response.ok() false. Done means identifying the cause and confirming that the generated page loads the bundle successfully.

Written by the indexing model from the issue text.