[17:04:31 ERROR]: Could not pass event AsyncPlayerChatEvent to Carstergames v1.0-SNAPSHOT
org.bukkit.event.EventException: null
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:306) ~[spigot.jar:git-Spigot-596221b-9a1fc1e]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[spigot.jar:git-Spigot-596221b-9a1fc1e]
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:499) [spigot.jar:git-Spigot-596221b-9a1fc1e]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:481) [spigot.jar:git-Spigot-596221b-9a1fc1e]
        at net.minecraft.server.v1_12_R1.PlayerConnection.chat(PlayerConnection.java:1307) [spigot.jar:git-Spigot-596221b-9a1fc1e]
        at net.minecraft.server.v1_12_R1.PlayerConnection.a(PlayerConnection.java:1245) [spigot.jar:git-Spigot-596221b-9a1fc1e]
        at net.minecraft.server.v1_12_R1.PacketPlayInChat$1.run(PacketPlayInChat.java:39) [spigot.jar:git-Spigot-596221b-9a1fc1e]
        at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) [?:1.8.0_241]
        at java.util.concurrent.FutureTask.run(Unknown Source) [?:1.8.0_241]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [?:1.8.0_241]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [?:1.8.0_241]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_241]
Caused by: java.lang.IllegalStateException: Asynchronous entity add!
        at org.spigotmc.AsyncCatcher.catchOp(AsyncCatcher.java:14) ~[spigot.jar:git-Spigot-596221b-9a1fc1e]
        at net.minecraft.server.v1_12_R1.World.addEntity(World.java:1016) ~[spigot.jar:git-Spigot-596221b-9a1fc1e]
        at net.minecraft.server.v1_12_R1.WorldServer.addEntity(WorldServer.java:1112) ~[spigot.jar:git-Spigot-596221b-9a1fc1e]
        at net.citizensnpcs.nms.v1_12_R1.util.NMSImpl.addEntityToWorld(NMSImpl.java:233) ~[?:?]
        at net.citizensnpcs.util.NMS.addEntityToWorld(NMS.java:42) ~[?:?]
        at net.citizensnpcs.npc.CitizensNPC.spawn(CitizensNPC.java:214) ~[?:?]
        at net.citizensnpcs.npc.CitizensNPC.spawn(CitizensNPC.java:190) ~[?:?]
        at customEntities.CustomZombie.onChatEvent(CustomZombie.java:21) ~[?:?]
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_241]
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_241]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_241]
        at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.8.0_241]
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:302) ~[spigot.jar:git-Spigot-596221b-9a1fc1e]
        ... 11 more