From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Mon, 29 Jun 2020 04:00:07 -0400
Subject: [PATCH] Don't fire unleash/dismount events from worldgen threads

Mojang can trigger this during worldgen and tries to fire bukkit events.

diff --git a/src/main/java/net/minecraft/server/Entity.java b/src/main/java/net/minecraft/server/Entity.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/Entity.java
+++ b/src/main/java/net/minecraft/server/Entity.java
@@ -0,0 +0,0 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, Ke
             // CraftBukkit start
             CraftEntity craft = (CraftEntity) entity.getBukkitEntity().getVehicle();
             Entity orig = craft == null ? null : craft.getHandle();
-            if (getBukkitEntity() instanceof Vehicle && entity.getBukkitEntity() instanceof LivingEntity) {
+            if (getBukkitEntity() instanceof Vehicle && entity.getBukkitEntity() instanceof LivingEntity && MCUtil.isMainThread()) { // Paper
                 VehicleExitEvent event = new VehicleExitEvent(
                         (Vehicle) getBukkitEntity(),
                         (LivingEntity) entity.getBukkitEntity(), !suppressCancellation // Paper
diff --git a/src/main/java/net/minecraft/server/EntityInsentient.java b/src/main/java/net/minecraft/server/EntityInsentient.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/EntityInsentient.java
+++ b/src/main/java/net/minecraft/server/EntityInsentient.java
@@ -0,0 +0,0 @@ public abstract class EntityInsentient extends EntityLiving {
         boolean flag1 = super.a(entity, flag);
 
         if (flag1 && this.isLeashed()) {
-            this.world.getServer().getPluginManager().callEvent(new EntityUnleashEvent(this.getBukkitEntity(), UnleashReason.UNKNOWN)); // CraftBukkit
+            if (MCUtil.isMainThread()) this.world.getServer().getPluginManager().callEvent(new EntityUnleashEvent(this.getBukkitEntity(), UnleashReason.UNKNOWN)); // CraftBukkit // Paper
             this.unleash(true, true);
         }