[SEVERE] null
org.bukkit.command.CommandException: Unhandled exception executing command 'ma' in plugin MobArena v0.94.4.47
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:42)
	at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:168)
	at org.bukkit.craftbukkit.CraftServer.dispatchCommand(CraftServer.java:386)
	at net.minecraft.server.NetServerHandler.handleCommand(NetServerHandler.java:777)
	at net.minecraft.server.NetServerHandler.chat(NetServerHandler.java:737)
	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:725)
	at org.getspout.spout.SpoutNetServerHandler.a(SpoutNetServerHandler.java:176)
	at net.minecraft.server.Packet3Chat.handle(Packet3Chat.java:33)
	at net.minecraft.server.NetworkManager.b(NetworkManager.java:226)
	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:100)
	at org.getspout.spout.SpoutNetServerHandler.a(SpoutNetServerHandler.java:552)
	at net.minecraft.server.NetworkListenThread.a(NetworkListenThread.java:78)
	at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:537)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:435)
	at net.minecraft.server.ThreadServerApplication.run(SourceFile:465)
Caused by: java.lang.NoSuchMethodError: org.bukkit.entity.Player.getActivePotionEffects()Ljava/util/Collection;
	at com.garbagemule.MobArena.PlayerData.<init>(PlayerData.java:24)
	at com.garbagemule.MobArena.ArenaStandard.storePlayerData(ArenaStandard.java:759)
	at com.garbagemule.MobArena.ArenaStandard.playerJoin(ArenaStandard.java:526)
	at com.garbagemule.MobArena.commands.user.JoinCommand.execute(JoinCommand.java:63)
	at com.garbagemule.MobArena.commands.CommandHandler.onCommand(CommandHandler.java:87)
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:40)
	... 14 more