Błąd ze skriptem

[21:12:14 ERROR]: null
org.bukkit.command.CommandException: Unhandled exception executing command 'sk' in plugin Skript v2.1.2
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46) ~[server.jar:git-Spigot-db6de12-18fbb24]
        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:141) ~[server.jar:git-Spigot-db6de12-18fbb24]
        at org.bukkit.craftbukkit.v1_8_R3.CraftServer.dispatchCommand(CraftServer.java:641) ~[server.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.PlayerConnection.handleCommand(PlayerConnection.java:1162) [server.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.PlayerConnection.a(PlayerConnection.java:997) [server.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.PacketPlayInChat.a(PacketPlayInChat.java:45) [server.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.PacketPlayInChat.a(PacketPlayInChat.java:1) [server.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.PlayerConnectionUtils$1.run(SourceFile:13) [server.jar:git-Spigot-db6de12-18fbb24]
        at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) [?:1.8.0_191]
        at java.util.concurrent.FutureTask.run(Unknown Source) [?:1.8.0_191]
        at net.minecraft.server.v1_8_R3.SystemUtils.a(SourceFile:44) [server.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:715) [server.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:374) [server.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:654) [server.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:557) [server.jar:git-Spigot-db6de12-18fbb24]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_191]
Caused by: java.lang.NoSuchMethodError: ch.njol.util.NonNullPair.getSecond()Ljava/lang/Object;
        at ch.njol.skript.command.Commands.loadCommand(Commands.java:379) ~[?:?]
        at ch.njol.skript.ScriptLoader.loadScript(ScriptLoader.java:462) ~[?:?]
        at ch.njol.skript.ScriptLoader.loadScripts(ScriptLoader.java:262) ~[?:?]
        at ch.njol.skript.SkriptCommand.onCommand(SkriptCommand.java:155) ~[?:?]
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ~[server.jar:git-Spigot-db6de12-18fbb24]
        ... 15 more

Problem ze skryptem na /ping 

Kod: 

command /ping [<player>]:
	trigger:
		if arg-1 is not set:
			send ""
			send "&7Twoj ping to  &c%player's ping% ms"
			send ""
			stop
		if arg-1 is set:
			if player has permission "terxan.ping":
				send ""
				send "&7Gracz &c%arg 1% &7posiada pingu &c%argument's ping% ms"
				send ""
				stop
			else:
				send "&cNie masz uprawnie�!"
				stop