HasMany Unload Exception

adapters.application.js

import DS from 'ember-data';
import Ember from 'ember';

export default DS.RESTAdapter.extend({
  namespace: 'api'
});

controllers.application.js

import Ember from 'ember';

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

models.asset-location.js

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

export default Model.extend({
  asset: belongsTo('asset'),
  order: attr('number')
});

models.asset.js

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

export default Model.extend({
  locations: hasMany('asset-location', { async: false }),
  locationsSorted: Ember.computed.sort('locations','locationsSortedBy'),
  locationsSortedBy: ['order:asc']
});

routes.index.js

import Ember from 'ember';

export default Ember.Route.extend({
  locations: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
  init(){
    $.mockjax({ url: '/api/assetLocations/0', responseText: { id: '0', asset: '1', order: '0' }});
    $.mockjax({ url: '/api/assetLocations/1', responseText: { id: '1', asset: '2', order: '1' }});
    $.mockjax({ url: '/api/assetLocations/2', responseText: { id: '2', asset: '3', order: '2' }});
    $.mockjax({ url: '/api/assetLocations/3', responseText: { id: '3', asset: '1', order: '3' }});
    $.mockjax({ url: '/api/assetLocations/4', responseText: { id: '4', asset: '2', order: '4' }});
    $.mockjax({ url: '/api/assetLocations/5', responseText: { id: '5', asset: '3', order: '5' }});
    $.mockjax({ url: '/api/assetLocations/6', responseText: { id: '6', asset: '1', order: '6' }});
    $.mockjax({ url: '/api/assetLocations/7', responseText: { id: '7', asset: '2', order: '7' }});
    $.mockjax({ url: '/api/assetLocations/8', responseText: { id: '8', asset: '3', order: '8' }});
    $.mockjax({ url: '/api/assetLocations/9', responseText: { id: '9', asset: '1', order: '9' }});
    $.mockjax({ url: '/api/assetLocations/10', responseText: { id: '10', asset: '2', order: '10' }});
  	$.mockjax({
      url: '/api/assets',
      responseText: [
        { id: '1' },
        { id: '2' },
        { id: '3' }
      ]
    });
  },
  model(){
  	return this.store.findAll('asset')
  },
  actions: {
    loadMoreLocation(){
      this.store.findRecord('asset-location', this.locations.pop());
    },
    unloadLocation(location){
    	this.store.unloadRecord(location);
    }
  }
});

serializers.application.js

import DS from 'ember-data';
import Ember from 'ember';

export default DS.JSONSerializer.extend({});

templates.application.hbs

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

templates.index.hbs

Asset Records:
{{#each model as |asset|}}
	<div>Asset {{asset.id}}:</div>
  <div>Locations:
  	<ol>
    	{{#each asset.locationsSorted as |location|}}
      		<li>{{location.id}} <input type="button" value="Unload" {{action 'unloadLocation' location}} /></li>
      {{/each}}
    </ol>
  </div>
{{/each}}
<input type="button" value="Load More Locations" {{action 'loadMoreLocation'}} /> 

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0",
    "jquery-mockjax": "https://cdnjs.cloudflare.com/ajax/libs/jquery-mockjax/1.6.2/jquery.mockjax.js"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}