When any player joins a LAN world/server and picks up any block that unlocks a new advancement, the player gets kicked from the world.
When the player joins the LAN world/server again, everything is fine. The block is in the inventory and new advancements can be unlocked without getting kicked.

The player who is hosting the LAN world or the server won't crash when picking up a block that unlocks a new advancement.

Also, when the LAN/server player picks up any block that doesn't unlock an advancement, like dirt, nothing happens and the player stays on the server.

The exception a NullPointerException. I couldn't find any logs.

Steps to reproduce:

1. Create new world
2. Open for LAN (Survival, Cheats OFF)
3. OR create fresh server
4. Join from other PC/account
5. Pick up any block that unlocks an advancement
6. Player gets kicked (crashes)
7. Join LAN world/server again, everything is fine