New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
	version: Ember.VERSION,
  name: 'Alex',
  capitalizedName: Ember.computed('name', function() {
    return Em.String.capitalize(this.get('name'));
  }),
  
  actions: {
    change(name) {
      this.set('name', name);
    }
  }
});

templates.application.hbs

<h1>{{version}}</h1>

name: {{name}} ({{capitalizedName}})

<hr>.

<button onclick={{action 'change' 'Ben'}}>Ben</button>
<button onclick={{action 'change' 'Sophie'}}>Sophie</button>
<button onclick={{action 'change' null}}>null</button>

<hr>

Try Ember 2.16.2 and 2.12.0. Notice the difference in behavior after clicking the `null` button.

twiddle.json

{
  "version": "0.13.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.16.2",
    "ember-template-compiler": "2.16.2",
    "ember-testing": "2.16.2"
  },
  "addons": {
    "ember-data": "2.16.3"
  }
}