fix EntityDismountEvent being fired on gen threads

Spigot-Server-Patches/Don-t-fire-unleash-dismount-events-from-worldgen-thr.patch

@@ -18,6 +18,15 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
                  VehicleExitEvent event = new VehicleExitEvent(
                          (Vehicle) getBukkitEntity(),
                          (LivingEntity) entity.getBukkitEntity(), !suppressCancellation // Paper
+@@ -0,0 +0,0 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, Ke
+             // CraftBukkit end
+             // Spigot start
+             org.spigotmc.event.entity.EntityDismountEvent event = new org.spigotmc.event.entity.EntityDismountEvent(entity.getBukkitEntity(), this.getBukkitEntity(), !suppressCancellation); // Paper
+-            Bukkit.getPluginManager().callEvent(event);
++            if (MCUtil.isMainThread()) Bukkit.getPluginManager().callEvent(event); // Paper
+             if (event.isCancelled()) {
+                 return false;
+             }
 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