title: standard dropdown arrow visible in firefox but not in chrome
body: <p>i got the follow custom dropdown</p>
  <p><img src="https://i.stack.imgur.com/U3ijL.png" alt="enter image description here" /></p>
  <p>which works like a charm in chrome but in firefox i get this:</p>
  <p><img src="https://i.stack.imgur.com/7IuJt.png" alt="enter image description here" /></p>
  <p>is there any possibility to hide that dropdown arrow in firefox?</p>