error

5:56:53 PM java.lang.IllegalArgumentException: Cannot set to an empty path
5:56:54 PM 	at org.apache.commons.lang.Validate.notEmpty(Validate.java:363)
5:56:54 PM 	at org.bukkit.configuration.MemorySection.set(MemorySection.java:156)
5:56:54 PM 	at org.bukkit.configuration.MemorySection.set(MemorySection.java:186)
5:56:54 PM 	at com.garbagemule.MobArena.util.config.Config.set(Config.java:345)
5:56:54 PM 	at com.garbagemule.MobArena.log.YMLSessionBuilder.reset(YMLSessionBuilder.java:109)
5:56:54 PM 	at com.garbagemule.MobArena.log.YMLSessionBuilder.<init>(YMLSessionBuilder.java:28)
5:56:54 PM 	at com.garbagemule.MobArena.ArenaImpl.<init>(ArenaImpl.java:174)
5:56:54 PM 	at com.garbagemule.MobArena.ArenaMasterImpl.loadArena(ArenaMasterImpl.java:519)
5:56:54 PM 	at com.garbagemule.MobArena.ArenaMasterImpl.loadArenas(ArenaMasterImpl.java:489)
5:56:54 PM 	at com.garbagemule.MobArena.ArenaMasterImpl.initialize(ArenaMasterImpl.java:242)
5:56:54 PM 	at com.garbagemule.MobArena.MobArena.onEnable(MobArena.java:81)
5:56:54 PM 	at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:215)
5:56:54 PM 	at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:336)
5:56:54 PM 	at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:381)
5:56:54 PM 	at org.bukkit.craftbukkit.CraftServer.loadPlugin(CraftServer.java:256)
5:56:54 PM 	at org.bukkit.craftbukkit.CraftServer.enablePlugins(CraftServer.java:238)
5:56:54 PM 	at net.minecraft.server.MinecraftServer.t(MinecraftServer.java:371)
5:56:54 PM 	at net.minecraft.server.MinecraftServer.a(MinecraftServer.java:358)
5:56:54 PM 	at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:187)
5:56:54 PM 	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:422)
5:56:54 PM 	at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)