confusion in variable name ?

To avoid this error : 

```
if (err) return stream.write({ type: data.type, err: err });
                                         ^
TypeError: Cannot read property 'type' of undefined
```

with this slice of code :

```
require('bigpipe').Pagelet.extend({
  name: 'test',
  view: 'view.ejs',
  streaming: true,
  get: function(render) {
    render(null, {});
  },
  post: function(body, files, next) {
    next(new Error('error'));
  }
}).on(module);
```