Netherbanpls

15:39:00 [SEVERE] null
org.bukkit.command.CommandException: Unhandled exception executing command 'nbban' in plugin NetherBanPls v1.0.7
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46)
        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:186)
        at org.bukkit.craftbukkit.v1_4_R1.CraftServer.dispatchCommand(CraftServer.java:541)
        at net.minecraft.server.v1_4_R1.PlayerConnection.handleCommand(PlayerConnection.java:995)
        at net.minecraft.server.v1_4_R1.PlayerConnection.chat(PlayerConnection.java:911)
        at net.minecraft.server.v1_4_R1.PlayerConnection.a(PlayerConnection.java:855)
        at net.minecraft.server.v1_4_R1.Packet3Chat.handle(Packet3Chat.java:44)
        at org.spigotmc.netty.NettyNetworkManager.b(NettyNetworkManager.java:152)
        at net.minecraft.server.v1_4_R1.PlayerConnection.d(PlayerConnection.java:115)
        at net.minecraft.server.v1_4_R1.ServerConnection.b(SourceFile:39)
        at org.spigotmc.netty.NettyServerConnection.b(NettyServerConnection.java:65)
        at net.minecraft.server.v1_4_R1.MinecraftServer.r(MinecraftServer.java:589)
        at net.minecraft.server.v1_4_R1.DedicatedServer.r(DedicatedServer.java:224)
        at net.minecraft.server.v1_4_R1.MinecraftServer.q(MinecraftServer.java:485)
        at net.minecraft.server.v1_4_R1.MinecraftServer.run(MinecraftServer.java:420)
        at net.minecraft.server.v1_4_R1.ThreadServerApplication.run(SourceFile:849)
Caused by: java.lang.NullPointerException
        at org.bukkit.craftbukkit.v1_4_R1.CraftServer.getWorld(CraftServer.java:840)
        at me.kiinho.NetherBanPls.NetherBan.onCommand(NetherBan.java:247)
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44)
        ... 15 more