Icons not displayed (optgroups) about emberx-select HOT 2 CLOSED

<div class="form-group">
  <label class="control-label col-sm-2" for="select-icon">Icon:</label>
  <div class="col-sm-2">
    <div class="btn-group">
      <button type="button" class="btn btn-default">
        <i class="fa fa-{{currentIcon}}"></i>&nbsp; {{currentIcon}}
      </button>
      <button type="button" class="btn btn-default dropdown-toggle" \
        data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
        <span class="caret"></span>
        <span class="sr-only">Toggle Dropdown</span>
      </button>
      <ul class="dropdown-menu">
        {{#each icons as |optgroup|}}
          <li class="disabled">
            <a href="#"><strong> - {{optgroup.group}} - </strong></a>
          </li>
          {{#each optgroup.icons as |icon|}}
            <li>
              <a href="#" {{action 'selectIcon' icon}}>
                <i class="fa fa-{{icon}}"></i>&nbsp; {{icon}}
              </a>
            </li>
          {{/each}}
        {{/each}}
      </ul>
    </div>
  </div>
</div>