title: Library tab in scenebuilder disappeared
body: <p>Clicked something and cant see the library tab anymore. Here is a picture of my scenebuilder:
  <a href="https://i.stack.imgur.com/haVVg.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/haVVg.png" alt="enter image description here" /></a></p>
  <p>As you can tell, library tab is missing. I've tried deleting and recreating the FXML to no avail.</p>