Players can desync from their mounts when jumping on a happy ghast

The bug

If the player is mounting a horse when standing on a happy ghast and decides to jump, this can sometimes lead to a desync between them and the horse.

How to reproduce

1. Summon a happy ghast.

2. Stand above the happy ghast, then summon a horse and saddle it.

/summon minecraft:horse ~ ~ ~ {Tame:1b}

1. Ride the horse and jump on the happy ghast.

Expected result

The player mounting the horse would jump on the ghast as expected, and without falling.

Observed result

The player falls slowly through the horse and the ghast.