template `calling set on undefined object`

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
	//contact: {},
	actions: {
		contactNameDidChange() {
			console.log(this.contact);
    }
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
value is binded to <span style="color: red">contact.contactname</span> - but <span style="color: red">contact</span> is undefined in controller
 <hr>
Enter name: {{input value=contact.contact_name input=(action 'contactNameDidChange')}}
<br><br>
<hr>
	check console
{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.11.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.10.2",
    "ember-data": "2.11.0",
    "ember-template-compiler": "2.10.2",
    "ember-testing": "2.10.2"
  },
  "addons": {}
}