BossBar doesnt despawn

Summary

Sometimes when a mob despawns very fast, directly after spawning, it doesn't remove the bossbar. So this happens if I have peaceful mode and spawn a mob like a zombie using a command and It also happens if you do mm reload And that mob from spawner is next to you.

Also - barRemove{name=<mob.name>} @self ~onDespawn doesn't help

Steps to reproduce

1. Create a Mob having a Bossbar
2. Set the server difficulty to peaceful.
3. Spawn the mob using /mm m spawn
4. The Mob will disappear, but the Bossbar doesn't go away (Server Side, so rejoin doesn't help)

Intended correct behavior

The Bossbar should go away