link-to with undefined href

templates.post.hbs

Displaying post {{model.id}}
<br>
{{#link-to 'user' model.user}}Link to user{{/link-to}}
<br>
{{#each model.comments as |comment|}}
  {{#link-to 'comment' comment}}Link to comment {{comment.id}}{{/link-to}}
{{/each}}

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  actions: {
    createRecords() {
      var user = this.store.createRecord('user', {
        name: 'DHH',
        slug: 'dhh'
      });
      var post = this.store.createRecord('post', {
        title: 'Rails is Omakase',
        slug: 'rails-is-omakase',
        user: user
      });
      var comment =  this.store.createRecord('comment', {
        body: '...',
        slug: 'comment-1',
        post: post
      });

      this.setProperties({
        user: user,
        post: post,
        comment: comment
      });

    }
  }
});

models.comment.js

import Model from "ember-data/model";
import attr from "ember-data/attr";
import { belongsTo, hasMany } from "ember-data/relationships";

export default Model.extend({
  body: attr(),
  slug: attr(),
});

models.post.js

import Model from "ember-data/model";
import attr from "ember-data/attr";
import { belongsTo, hasMany } from "ember-data/relationships";

export default Model.extend({
	title: attr(),
  slug: attr(),
  user: belongsTo(),
  comments: hasMany(),
});

models.user.js

import Model from "ember-data/model";
import attr from "ember-data/attr";
import { belongsTo, hasMany } from "ember-data/relationships";

export default Model.extend({
  name: attr(),
  slug: attr(),
});

router.js

import Ember from 'ember';
import config from './config/environment';

const Router = Ember.Router.extend({
  location: 'none',
  rootURL: config.rootURL
});

Router.map(function() {
  this.route('user', {path: '/user/:slug'});
  this.route('post', {path: '/post/:slug'});
  this.route('comment', {path: '/comment/:slug'});
});

export default Router;

routes.application.js

import Ember from 'ember';

export default Ember.Route.extend({
});

routes.post.js

import Ember from 'ember';

export default Ember.Route.extend({
  model(params) {
    return this.store.findRecord(
      'post',
      params.id,
      {include: 'user,comments'}
    );
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>

<a href="#" {{action 'createRecords'}}>First, create the records</a>
<br>
{{#link-to 'post' post}}Then, go to the post page{{/link-to}}

{{outlet}}

twiddle.json

{
  "version": "0.10.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.6.0",
    "ember-data": "2.6.1",
    "ember-template-compiler": "2.6.0"
  },
  "addons": {}
}