SkyWars Error

[15:21:39] [Server thread/ERROR]: **** THIS IS NOT AN ISSUE TO DO WITH PER WORLD PLUGINS ****
Could not pass event PlayerInteractEvent to SkyWars v1.3.8.6
org.bukkit.event.EventException
	at us.Myles.PWP.TransparentListeners.PerWorldPluginLoader$1.execute(PerWorldPluginLoader.java:122) ~[?:?]
	at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[craftbukkit.jar:git-Spigot-d97e08b-880a532]
	at us.Myles.PWP.TransparentListeners.PWPRegisteredListener.callEvent(PWPRegisteredListener.java:30) [PerWorldPlugins_1.8.8_Java_7.jar:?]
	at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [craftbukkit.jar:git-Spigot-d97e08b-880a532]
	at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [craftbukkit.jar:git-Spigot-d97e08b-880a532]
	at org.bukkit.craftbukkit.v1_8_R3.event.CraftEventFactory.callPlayerInteractEvent(CraftEventFactory.java:227) [craftbukkit.jar:git-Spigot-d97e08b-880a532]
	at net.minecraft.server.v1_8_R3.PlayerInteractManager.interact(PlayerInteractManager.java:463) [craftbukkit.jar:git-Spigot-d97e08b-880a532]
	at net.minecraft.server.v1_8_R3.PlayerConnection.a(PlayerConnection.java:759) [craftbukkit.jar:git-Spigot-d97e08b-880a532]
	at net.minecraft.server.v1_8_R3.PacketPlayInBlockPlace.a(PacketPlayInBlockPlace.java:52) [craftbukkit.jar:git-Spigot-d97e08b-880a532]
	at net.minecraft.server.v1_8_R3.PacketPlayInBlockPlace.a(PacketPlayInBlockPlace.java:1) [craftbukkit.jar:git-Spigot-d97e08b-880a532]
	at net.minecraft.server.v1_8_R3.PlayerConnectionUtils$1.run(SourceFile:13) [craftbukkit.jar:git-Spigot-d97e08b-880a532]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) [?:1.7.0_79]
	at java.util.concurrent.FutureTask.run(FutureTask.java:262) [?:1.7.0_79]
	at net.minecraft.server.v1_8_R3.SystemUtils.a(SourceFile:44) [craftbukkit.jar:git-Spigot-d97e08b-880a532]
	at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:714) [craftbukkit.jar:git-Spigot-d97e08b-880a532]
	at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:374) [craftbukkit.jar:git-Spigot-d97e08b-880a532]
	at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:653) [craftbukkit.jar:git-Spigot-d97e08b-880a532]
	at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:556) [craftbukkit.jar:git-Spigot-d97e08b-880a532]
	at java.lang.Thread.run(Thread.java:745) [?:1.7.0_79]
Caused by: java.lang.NullPointerException
	at ak.CookLoco.SkyWars.arena.Arena.addPlayer(Arena.java:582) ~[?:?]
	at ak.CookLoco.SkyWars.arena.sign.SignManager.onSignClick(SignManager.java:304) ~[?:?]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.7.0_79]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[?:1.7.0_79]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.7.0_79]
	at java.lang.reflect.Method.invoke(Method.java:606) ~[?:1.7.0_79]
	at us.Myles.PWP.TransparentListeners.PerWorldPluginLoader$1.execute(PerWorldPluginLoader.java:120) ~[?:?]
	... 18 more