selectric.js nesting bug

HTML

<script src="https://selectric.js.org/jquery.selectric.min.js"></script>
<link rel="stylesheet" href="https://selectric.js.org/selectric.css">
<select class='selectric' multiple>
  <option  value="">Please choose...</option>
  <optgroup label="L1">
    <option value="ant">Ant</option>
    <option value="cat">Cat</option>
    <option value="dog">Dog</option>
  </optgroup>
</select>

JavaScript

$('.selectric').selectric();
  
  $('.selectric option[value="cat"]').prop('selected', true)

  // when uncommit this, you see Ant & Cat...
  //$('.selectric option[value="dog"]').prop('selected', true)
  
  $('.selectric').selectric('refresh')