undefined moment

controllers.application.js

import Ember from 'ember';

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

templates.application.hbs

<h3>allow-empty=false</h3>
null: {{moment-format null}}
<br>
empty string: {{moment-format ''}}
<br>
undefined: {{moment-format undefined}}
<br>

<h3>allow-empty=true</h3>
null: {{moment-format null allow-empty=true}}
<br>
empty string: {{moment-format '' allow-empty=true}}
<br>
undefined: {{moment-format undefined allow-empty=true}}
<br>

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2",
    "ember-moment": "latest"
  }
}