Server crash after player leaves (sometimes)

[BasToTheMax]

Sometimes, when a player (can be a moderator in vanish or a normal player without being in vanish) leaves the server, the server crashes with the following error:

Time: 2026-01-19 18:57:56
Description: Exception in server tick loop

java.lang.NullPointerException: Cannot invoke "net.minecraft.class_3222.method_51469()" because "actor" is null
	at knot//me.drex.vanish.util.VanishManager.canSeePlayer(VanishManager.java:89)
	at knot//me.drex.vanish.api.VanishAPI.canSeePlayer(VanishAPI.java:55)
	at knot//net.minecraft.class_8609.handler$edm000$vanish$modifyPackets(class_8609.java:4558)
	at knot//net.minecraft.class_8609.method_52391(class_8609.java)
	at knot//net.minecraft.class_3244.method_52391(class_3244.java:2333)
	at knot//net.minecraft.class_8609.method_14364(class_8609.java:159)
	at knot//net.minecraft.class_3324.method_14581(class_3324.java:498)
	at knot//com.fibermc.essentialcommands.playerdata.PlayerDataManager.tick(PlayerDataManager.java:150)
	at knot//com.fibermc.essentialcommands.playerdata.PlayerDataManager.lambda$init$0(PlayerDataManager.java:66)
	at knot//net.fabricmc.fabric.api.event.lifecycle.v1.ServerTickEvents.lambda$static$2(ServerTickEvents.java:55)
	at knot//net.minecraft.server.MinecraftServer.handler$bgg000$fabric-lifecycle-events-v1$onEndTick(MinecraftServer.java:6353)
	at knot//net.minecraft.server.MinecraftServer.method_3748(MinecraftServer.java:1041)
	at knot//net.minecraft.class_3176.method_3748(class_3176.java:321)
	at knot//net.minecraft.server.MinecraftServer.method_29741(MinecraftServer.java:772)
	at knot//net.minecraft.server.MinecraftServer.method_29739(MinecraftServer.java:297)
	at java.base/java.lang.Thread.run(Thread.java:1447)

This has happened a few times now, but I have not been able to reproduce it in a stable way.
And has happened with both vanished and unvanished players.
Only happens when a player leaves the server.

Server version: fabric 1.21.9
Mod version: 1.6.4, will update to 1.6.6 and see if it still happens.

[DrexHD]

Yes, please check version 1.6.6, it is very likely that it will fix this issue!

[DrexHD]

Didn't mean to close yet 😅

[BasToTheMax]

I have updated to 1.6.6
It might take a while for me to post the results as this happens very rarely (and mainly when I'm sleeping, for some reason)