Major glitches when you try to change fullscreen status when the carousel is moving

If you go the [demo](https://flickity.metafizzy.co/options.html#fullscreen), click the next button on the carousel, and then immediately click the fullscreen button, instead of seeing the fullscreen carousel, you'll see a black image. Similarly, if you drag the carousel while it's in fullscreen and then click the button to exit, the carousel image will disappear.

This bug makes this functionality unusable, and any insight into why it might be happening would be greatly appreciated.

Start with the fullscreen demo linked in the issue and reproduce both transitions: entering fullscreen while the carousel moves and exiting fullscreen after dragging. Inspect the fullscreen and carousel transition entry points involved in those actions. Done means the carousel image remains visible and correctly displayed in both cases.

Written by the indexing model from the issue text.