zarena internal error

2013-07-11 07:36:14 [INFO] LastTulare issued server command: /za alive
2013-07-11 07:36:14 [SEVERE] null
org.bukkit.command.CommandException: Unhandled exception executing command 'za' in plugin ZArena v0.7.2
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46)
	at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:189)
	at org.bukkit.craftbukkit.v1_6_R2.CraftServer.dispatchCommand(CraftServer.java:523)
	at net.minecraft.server.v1_6_R2.PlayerConnection.handleCommand(PlayerConnection.java:964)
	at net.minecraft.server.v1_6_R2.PlayerConnection.chat(PlayerConnection.java:882)
	at net.minecraft.server.v1_6_R2.PlayerConnection.a(PlayerConnection.java:839)
	at net.minecraft.server.v1_6_R2.Packet3Chat.handle(SourceFile:49)
	at net.minecraft.server.v1_6_R2.NetworkManager.b(NetworkManager.java:296)
	at net.minecraft.server.v1_6_R2.PlayerConnection.e(PlayerConnection.java:118)
	at net.minecraft.server.v1_6_R2.ServerConnection.b(SourceFile:37)
	at net.minecraft.server.v1_6_R2.DedicatedServerConnection.b(SourceFile:30)
	at net.minecraft.server.v1_6_R2.MinecraftServer.t(MinecraftServer.java:590)
	at net.minecraft.server.v1_6_R2.DedicatedServer.t(DedicatedServer.java:226)
	at net.minecraft.server.v1_6_R2.MinecraftServer.s(MinecraftServer.java:486)
	at net.minecraft.server.v1_6_R2.MinecraftServer.run(MinecraftServer.java:419)
	at net.minecraft.server.v1_6_R2.ThreadServerApplication.run(SourceFile:582)
Caused by: java.lang.StringIndexOutOfBoundsException: String index out of range: -2
	at java.lang.String.substring(Unknown Source)
	at com.github.zarena.commands.CommandHandler.listAlive(CommandHandler.java:206)
	at com.github.zarena.commands.ZACommands.onCommand(ZACommands.java:70)
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44)
	... 15 more
2013-07-11 07:36:37 [INFO] [0;31;1mStarting world save![m
2013-07-11 07:36:37 [INFO] [ServerSave] Starting Save!
2013-07-11 07:36:38 [INFO] [0;31;1mSave Complete![m
2013-07-11 07:36:38 [INFO] [ServerSave] Save complete!
2013-07-11 07:36:39 [INFO] [0;35;1m[Tip][0;37;1m [0;35;22mType [0;33;22m/bal [0;35;22mto see how much money you have. [0;33;22m/pay USERNAME AMOUNT [0;35;22mto pay another player. [0;33;22m/econ [0;35;22mfor more options[m
2013-07-11 07:36:44 [INFO] LastTulare issued server command: /za session
2013-07-11 07:36:44 [SEVERE] null
org.bukkit.command.CommandException: Unhandled exception executing command 'za' in plugin ZArena v0.7.2
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46)
	at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:189)
	at org.bukkit.craftbukkit.v1_6_R2.CraftServer.dispatchCommand(CraftServer.java:523)
	at net.minecraft.server.v1_6_R2.PlayerConnection.handleCommand(PlayerConnection.java:964)
	at net.minecraft.server.v1_6_R2.PlayerConnection.chat(PlayerConnection.java:882)
	at net.minecraft.server.v1_6_R2.PlayerConnection.a(PlayerConnection.java:839)
	at net.minecraft.server.v1_6_R2.Packet3Chat.handle(SourceFile:49)
	at net.minecraft.server.v1_6_R2.NetworkManager.b(NetworkManager.java:296)
	at net.minecraft.server.v1_6_R2.PlayerConnection.e(PlayerConnection.java:118)
	at net.minecraft.server.v1_6_R2.ServerConnection.b(SourceFile:37)
	at net.minecraft.server.v1_6_R2.DedicatedServerConnection.b(SourceFile:30)
	at net.minecraft.server.v1_6_R2.MinecraftServer.t(MinecraftServer.java:590)
	at net.minecraft.server.v1_6_R2.DedicatedServer.t(DedicatedServer.java:226)
	at net.minecraft.server.v1_6_R2.MinecraftServer.s(MinecraftServer.java:486)
	at net.minecraft.server.v1_6_R2.MinecraftServer.run(MinecraftServer.java:419)
	at net.minecraft.server.v1_6_R2.ThreadServerApplication.run(SourceFile:582)
Caused by: java.lang.StringIndexOutOfBoundsException: String index out of range: -2
	at java.lang.String.substring(Unknown Source)
	at com.github.zarena.commands.CommandHandler.listSession(CommandHandler.java:216)
	at com.github.zarena.commands.ZACommands.onCommand(ZACommands.java:84)
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44)
	... 15 more