Waypoint packet is handled by network thread instead of render thread, causing crash

Crash report provided by Viradex at Mojiracord.

Steps to Reproduce

1. Have a lot of waypoints

2. Move around

3. Client crashes

Code Analysis (official mappings)

ClientGamePacketListener#handleWaypoint does not call ensureRunningOnSameThread (which is used to handle the ClientboundTrackedWaypointPacket on render thread). This means the game handles it in Netty thread. This causes concurrent modification of waypoint map, causing crash when the packet arrives while waypoint is being sorted by render thread.