Solved 1.15.2 Spawn Entity(NMS) Error

If use world.addEntity it will have an error.
I was troubled by this for about two hours.

Code (error (Unknown Language)):

[21:42:44 ERROR]: Attempted Double World add on FollowPet['Wolf'/62, uuid='70f0da2e-6551-4db4-a3d7-787fa07a82a9', l='world', x=-278.50, y=63.00, z=226.50, cx=-18, cz=14, tl=0, v=true, d=false]
java.lang.Throwable: null
        at net.minecraft.server.v1_15_R1.WorldServer.addEntity0(WorldServer.java:1164) ~[Paper-1.15.2-b90.jar:git-Paper-89]
        at net.minecraft.server.v1_15_R1.WorldServer.addEntity(WorldServer.java:1096) ~[Paper-1.15.2-b90.jar:git-Paper-89]
...
 

Code (Java):

public static void registerEntity() {
    String customName = "custom_wolf";
    Map<String, Type<?>> types = (Map<String, Type<?>>) DataConverterRegistry.a()
            .getSchema(DataFixUtils.makeKey(SharedConstants.getGameVersion().getWorldVersion()))
            .findChoiceType(DataConverterTypes.ENTITY).types();
    types.put("minecraft:" + customName, types.get("minecraft:wolf"));
    EntityTypes.a<Entity> a = EntityTypes.a.a(FollowPet::new, EnumCreatureType.MONSTER);
    entityTypes = IRegistry.a(IRegistry.ENTITY_TYPE, customName, a.a(customName));
}

public static Wolf getWolf(Player player, Location location) {
    WorldServer world = ((CraftWorld) player.getWorld()).getHandle();
    Entity entity = entityTypes.spawnCreature(world,
            null,
            null,
            null,
            new BlockPosition(location.getX(), location.getY(), location.getZ()), EnumMobSpawn.EVENT,
            false,
            false);
    entity.setInvisible(true);
    world.addEntity(entity, CreatureSpawnEvent.SpawnReason.CUSTOM);
    return  (Wolf) entity.getBukkitEntity();
}
 

 

Hello?

 

I'm sorry, I'm not proficient in English, I don't understand it through machine translation. If this line is deleted, the entity will not be spawn.