The bug

When killed the mount, the passenger do not immediately dismount, until the body disappears.

But the experience and items will drop immediately.

Steps to reproduce

1. Summon a mob riding other mob

   /summon minecraft:ravager ~ ~ ~ {Health:1f,Passengers:[{id:pillager}]}

1. kill the mount

-->  The pillager do not dismount, until the ravager's body disappears.

Expected behavior

The passenger dismounts immediately when the mount dies.

Observed behavior

The passenger keeps riding the dying mob until the body disappears.