JSFiddle - React, Tailwind, and code Playground

HTML

<div>
I should be visible (red)
  <ul>
    <li>one</li>
  </ul>
</div>

<div>
I should be hidden (blue)
  <ul></ul>
</div>

CSS

div{border:1px solid red;}
div:has(ul:empty){
  border:1px solid blue;
}