npx express-generator does not follow error recommendations

https://expressjs.com/en/guide/error-handling.html#the-default-error-handler

> So when you add a custom error handler, you must delegate to the default Express error handler, when the headers have already been sent to the client

```
function errorHandler (err, req, res, next) {
if (res.headersSent) {
return next(err)
}
res.status(500)
res.render('error', { error: err })
}
```

The `express-generator` does not follow the recommendation:

```
$ npx express-generator
$ grep -A 10 '// error handler' app.js
// error handler
app.use(function(err, req, res, next) {
// set locals, only providing error in development
res.locals.message = err.message;
res.locals.error = req.app.get('env') === 'development' ? err : {};

// render the error page
res.status(err.status || 500);
res.render('error');
});
```