Bukkit

What is the issue?
Plugin does not work....
Please provide any additional information below.

In console: (back to front (sorry))

[13:37:00 INFO]: cm8263 lost connection: Disconnected
2015-01-15T13:36:57.805103875Z     ... 13 more
2015-01-15T13:36:57.805103875Z     at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ~[server.jar:git-Spigot-1649]
2015-01-15T13:36:57.805103875Z     at vc.pvp.skywars.commands.MainCommand.onCommand(MainCommand.java:53) ~[?:?]
2015-01-15T13:36:57.805103875Z     at vc.pvp.skywars.commands.LeaveCommand.onCommand(LeaveCommand.java:18) ~[?:?]
2015-01-15T13:36:57.805103875Z Caused by: java.lang.NullPointerException
2015-01-15T13:36:57.805103875Z     at net.minecraft.server.v1_7_R4.ThreadServerApplication.run(SourceFile:628) [server.jar:git-Spigot-1649]
2015-01-15T13:36:57.805103875Z     at net.minecraft.server.v1_7_R4.MinecraftServer.run(MinecraftServer.java:490) [server.jar:git-Spigot-1649]
2015-01-15T13:36:57.805103875Z     at net.minecraft.server.v1_7_R4.MinecraftServer.u(MinecraftServer.java:584) [server.jar:git-Spigot-1649]
2015-01-15T13:36:57.805103875Z     at net.minecraft.server.v1_7_R4.DedicatedServer.v(DedicatedServer.java:289) [server.jar:git-Spigot-1649]
2015-01-15T13:36:57.805103875Z     at net.minecraft.server.v1_7_R4.MinecraftServer.v(MinecraftServer.java:734) [server.jar:git-Spigot-1649]
2015-01-15T13:36:57.805103875Z     at net.minecraft.server.v1_7_R4.ServerConnection.c(ServerConnection.java:81) [server.jar:git-Spigot-1649]
2015-01-15T13:36:57.805103875Z     at net.minecraft.server.v1_7_R4.NetworkManager.a(NetworkManager.java:186) [server.jar:git-Spigot-1649]
2015-01-15T13:36:57.805103875Z     at net.minecraft.server.v1_7_R4.PacketPlayInChat.handle(PacketPlayInChat.java:65) [server.jar:git-Spigot-1649]
2015-01-15T13:36:57.805103875Z     at net.minecraft.server.v1_7_R4.PacketPlayInChat.a(PacketPlayInChat.java:28) [server.jar:git-Spigot-1649]
2015-01-15T13:36:57.805103875Z     at net.minecraft.server.v1_7_R4.PlayerConnection.a(PlayerConnection.java:880) [server.jar:git-Spigot-1649]
2015-01-15T13:36:57.805103875Z     at net.minecraft.server.v1_7_R4.PlayerConnection.handleCommand(PlayerConnection.java:1043) [server.jar:git-Spigot-1649]
2015-01-15T13:36:57.805103875Z     at org.bukkit.craftbukkit.v1_7_R4.CraftServer.dispatchCommand(CraftServer.java:767) ~[server.jar:git-Spigot-1649]
2015-01-15T13:36:57.805103875Z     at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:181) ~[server.jar:git-Spigot-1649]
2015-01-15T13:36:57.805103875Z     at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46) ~[server.jar:git-Spigot-1649]
2015-01-15T13:36:57.805103875Z org.bukkit.command.CommandException: Unhandled exception executing command 'sw' in plugin SkyWars v1.1-m16
2015-01-15T13:36:57.805103875Z >