Test Mut Safari Bug

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  val: true
});

templates.application.hbs

Current Val: {{val}}

<button onclick={{action (mut val) false}}>
  Set val false
 </button>
 
 <button onclick={{action (mut val) true}}>
  Set val true
 </button>

twiddle.json

{
  "version": "0.9.3",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "canary",
    "ember-data": "2.6.1",
    "ember-template-compiler": "canary"
  }
}