title: Dropdown displaying top and not in the bottom in Firefox
body: <p>I am using Bootstrap 4 Cards and the framework select2. I have a basic dropdown select inside a card-body but this, display to the top in Firefox. However, works fine in Google Chrome. I cant understand why. How can I make to display bottom without set height?</p>
  
  <pre><code>   &lt;div class="card-body"&gt;
      &lt;div class="form-row"&gt;
        &lt;!--&lt;label for="email" class="mr-sm-2"&gt;CIF:&lt;/label&gt;
        &lt;input type="email" class="form-control mb-2 mr-sm-2" id="email"&gt;--&gt;
  
  
        &lt;select class="js-example-responsive js-example-basic-single" style="width: 50%"&gt;
  
          &lt;optgroup label="..."&gt;
            &lt;option&gt;...&lt;/option&gt;
            ...
        &lt;/select&gt;
  
        &lt;script&gt;
          $(document).ready(function () {
            $('.js-example-basic-single').select2();
          });
        &lt;/script&gt;
      &lt;/div&gt;
    &lt;/div&gt;
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/HtVrp.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/HtVrp.png" alt="enter image description here"></a></p>
  
  <p>Thanks.</p>