Ember Error while processing route: index Assertion Failed: Unable to find fixtures for model

I have my index page where i show a list of invoices where the user can click to create and edit them, i am using DS.FixtureAdapter in my adapter

The problem is that i get this error

Error while processing route: index Assertion Failed: Unable to find fixtures for model

If in my model i reopen the class like this, everything works fine

Invoice.reopenClass({
  FIXTURES: [
    {
      id          : '1',
      name        : 'Invoice num 1',
      transactions: [1]
    }
  ]
});

So i assume that i am doing something wrong in my template where i am saying if there are not invoices show me "no invoices..."

<div class="row">
    <div class="large-6 columns">
      <h3>View Invoices</h3>
        <ul class="invoices-listing">
            {{#each invoice in model}}
            <li>
                {{#link-to "invoices.show" invoice}}
                    {{invoice.name}}
                {{/link-to}}
            </li>
            {{else}}
            <li>no invoices… :(</li>
            {{/each}}
        </ul>
    </div>
    <div class="large-6 columns">
      <h3>Edit Invoices</h3>
        <ul class="invoices-listing">
            {{#each invoice in model}}
            <li>
                {{#link-to "invoices.edit" invoice}}
                    {{invoice.name}}
                {{/link-to}}
            </li>
            {{else}}
            <li>no invoices… :(</li>
            {{/each}}
        </ul>
    </div>
    <div class="large-12 columns">
      Invoices: {{InvoicesCount}}
    </div>
    <div class="large-12 columns">
      {{#link-to "Invoices.create" class="create-btn"}} Add Invoice {{/link-to}}
    </div>
</div>

Routes Index.js

import Ember from 'ember';

export default Ember.Route.extend({
  model: function(){
    return this.store.find('fattura');
  }
});

This looks like a problem only when i start the ember server because for instance if i start creating and deleting invoices and i want to delete all of them the index page shows correctly "no invoices..."