World Borders (Packet)

I'm trying to create different world borders for each player and their island, but i'm getting this error:

Error (open) Error (close)

Code:

[12:34:34 ERROR]: Could not pass event IslandEnterEvent to Bordes v1.0
org.bukkit.event.EventException: null
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:306) ~[Spigot.jar:git-Spigot-edd0396-2a927e8]
    at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[Spigot.jar:git-Spigot-edd0396-2a927e8]
    at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:499) [Spigot.jar:git-Spigot-edd0396-2a927e8]
    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:484) [Spigot.jar:git-Spigot-edd0396-2a927e8]
    at com.wasteofplastic.askyblock.listeners.PlayerEvents.onPlayerJoin(PlayerEvents.java:233) [askyblock.jar:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_65]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_65]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_65]
    at java.lang.reflect.Method.invoke(Method.java:497) ~[?:1.8.0_65]
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:302) [Spigot.jar:git-Spigot-edd0396-2a927e8]
    at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) [Spigot.jar:git-Spigot-edd0396-2a927e8]
    at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:499) [Spigot.jar:git-Spigot-edd0396-2a927e8]
    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:484) [Spigot.jar:git-Spigot-edd0396-2a927e8]
    at net.minecraft.server.v1_12_R1.PlayerList.onPlayerJoin(PlayerList.java:346) [Spigot.jar:git-Spigot-edd0396-2a927e8]
    at net.minecraft.server.v1_12_R1.PlayerList.a(PlayerList.java:166) [Spigot.jar:git-Spigot-edd0396-2a927e8]
    at net.minecraft.server.v1_12_R1.LoginListener.b(LoginListener.java:159) [Spigot.jar:git-Spigot-edd0396-2a927e8]
    at net.minecraft.server.v1_12_R1.LoginListener.e(LoginListener.java:57) [Spigot.jar:git-Spigot-edd0396-2a927e8]
    at net.minecraft.server.v1_12_R1.NetworkManager.a(NetworkManager.java:233) [Spigot.jar:git-Spigot-edd0396-2a927e8]
    at net.minecraft.server.v1_12_R1.ServerConnection.c(ServerConnection.java:140) [Spigot.jar:git-Spigot-edd0396-2a927e8]
    at net.minecraft.server.v1_12_R1.MinecraftServer.D(MinecraftServer.java:845) [Spigot.jar:git-Spigot-edd0396-2a927e8]
    at net.minecraft.server.v1_12_R1.DedicatedServer.D(DedicatedServer.java:406) [Spigot.jar:git-Spigot-edd0396-2a927e8]
    at net.minecraft.server.v1_12_R1.MinecraftServer.C(MinecraftServer.java:679) [Spigot.jar:git-Spigot-edd0396-2a927e8]
    at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:577) [Spigot.jar:git-Spigot-edd0396-2a927e8]
    at java.lang.Thread.run(Thread.java:745) [?:1.8.0_65]
Caused by: java.lang.NullPointerException
    at net.minecraft.server.v1_12_R1.PacketPlayOutWorldBorder.<init>(PacketPlayOutWorldBorder.java:22) ~[Spigot.jar:git-Spigot-edd0396-2a927e8]
    at com.armandozetaxx.Bordes.Eventos.SkyblockEvents.sendWorldBorder(SkyblockEvents.java:73) ~[?:?]
    at com.armandozetaxx.Bordes.Eventos.SkyblockEvents.onIslandEntry(SkyblockEvents.java:38) ~[?:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_65]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_65]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_65]
    at java.lang.reflect.Method.invoke(Method.java:497) ~[?:1.8.0_65]
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:302) ~[Spigot.jar:git-Spigot-edd0396-2a927e8]
    ... 23 more

Here is the code of the class:

Code (open) Code (close)

Code:

package com.armandozetaxx.Bordes.Eventos;

import java.lang.reflect.Method;

import org.bukkit.Bukkit;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;

import com.wasteofplastic.askyblock.ASkyBlockAPI;
import com.wasteofplastic.askyblock.Island;
import com.wasteofplastic.askyblock.events.IslandEnterEvent;
import com.wasteofplastic.askyblock.events.IslandNewEvent;

import net.minecraft.server.v1_12_R1.PacketPlayOutWorldBorder;
import net.minecraft.server.v1_12_R1.PacketPlayOutWorldBorder.EnumWorldBorderAction;
import net.minecraft.server.v1_12_R1.WorldBorder;


public class SkyblockEvents implements Listener {

    @EventHandler
    public void onIslandEntry(IslandEnterEvent e){
        Player p = Bukkit.getPlayer(e.getPlayer());
        Island is = ASkyBlockAPI.getInstance().getIslandAt(e.getIslandLocation());
        int size =is.getProtectionSize();
        double x = is.getCenter().getX();
        double z = is.getCenter().getZ();
        sendWorldBorder(p, x, z, size);
    }
  
    public static void sendPacket(Player player, Object packet){
        try {
            Object playerHandle = player.getClass().getMethod("getHandle").invoke(player);
            Object connection = playerHandle.getClass().getField("playerConnection").get(playerHandle);
            Method sendPacket = connection.getClass().getMethod("sendPacket", getServerClass("Packet"));

            sendPacket.invoke(connection, packet);


        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static Class<?> getServerClass(String afterPackage){
        String servPack = Bukkit.getServer().getClass().getPackage().getName().split("\\.")[3];

        try {
            return Class.forName("net.minecraft.server." + servPack + "." + afterPackage);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
            return null;
        }
    }


    public static void sendWorldBorder(Player player, double x, double z, int size){
        WorldBorder border = new WorldBorder();
        border.setCenter(x, z);
        border.setSize(size);

        PacketPlayOutWorldBorder packet = new PacketPlayOutWorldBorder(border, EnumWorldBorderAction.INITIALIZE);

        sendPacket(player, packet);
    }

}

Hope somebody can explain me what is the error and how to fixed, thank you for your time.