Desync when a player rides a horse riding another mob, and that mob dies

If a horse is riding a mob, and that mob gets killed, players riding that horse get kicked off the horse client-side but not server-side.

To reproduce

1. Run the following command:

   /summon husk ~ ~ ~ {Passengers:[{id:"minecraft:horse",Tame:1b}]}

2. Place a block of TNT next to the husk
3. Ignite that TNT
4. Mount the horse
5. When the husk dies, you get dismounted
6. Walk away
7. Sneak
   → You get teleported back to the horse

Video

Minecraft 1.16 Release Candidate 1 - Singleplayer 2020-06-20 19-31-52.mp4