Fix race condition when unmounting modal while opening it

[elliottkember]

Motivation

When a Bottom Sheet is animating in, its currentIndexRef is -1, and is not set to 0 until the animation finishes. This means that if the component is unmounted while it's still opening, the modal sticks around on screen and is uncloseable. This results in a zombie bottom sheet modal that can never be removed! 🧟

To replicate:

  const [showModal, setShowModal] = useState(false);
  useEffect(() => {
    setShowModal(true);
    setTimeout(() => {
      setShowModal(false);
    }, 200);
  }, []);

...

{showModal && <BottomSheetPullUp />}

Changes:

• adds an animatingRef which tracks the status of the component's entry animation.
• checks this animatingRef when minimizing the modal
• animatingRef is initialized as false animateOnMount is set to false!
• uses onAnimate to set animatingRef = true when animating

[github-actions]

This PR is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 10 days.

[elliottkember]

I think this is still valid!

[iqorlobanov]

Fixed here: #2564