Installing this addon breaks application controller

[jacobq]

I don't quite understand why this is the case, but this cost me many hours of debug time to find, so I wanted to make people aware of it. To reproduce the problem do the following:

1. ember new demo-app
2. cd demo-app
3. Edit package.json to remove ember-welcome-page
4. ember generate controller application
5. Edit app/controllers/application.js to display a message when it gets initialized. For example:

import Ember from 'ember';

export default Ember.Controller.extend({
    init() {
        this._super(...arguments);
        alert('working!!!');
        console.log("WORKING!!!");
    }
});

1. ember server (see that it works)
2. ember install ember-cli-template-debug
3. ember server (see that it no longer works -- no message)