The Express render callback html argument is being ignored. It looks like somebody tried to hack a fix by calling render a second time, but the correct thing to do with a callback is to send the html. Otherwise you have to specify the scope twice.
Thus this should be written as: https://github.com/DaftMonk/generator-angular-fullstack/blob/canary/app/templates/server/components/errors/index.js
res.render(viewFilePath, { }, function (err, html) {
if (err) { return res.json(result, result.status); }
res.send(html);
});