Server.log

[SEVERE] Could not pass event EntityDamageByEntityEvent to LeveledMobs v1.0
org.bukkit.event.EventException
	at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:427)
	at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
	at org.bukkit.plugin.TimedRegisteredListener.callEvent(TimedRegisteredListener.java:47)
	at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:478)
	at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:463)
	at org.bukkit.craftbukkit.v1_6_R3.event.CraftEventFactory.callEvent(CraftEventFactory.java:94)
	at org.bukkit.craftbukkit.v1_6_R3.event.CraftEventFactory.callEntityDamageEvent(CraftEventFactory.java:398)
	at org.bukkit.craftbukkit.v1_6_R3.event.CraftEventFactory.handleEntityDamageEvent(CraftEventFactory.java:423)
	at net.minecraft.server.v1_6_R3.EntityLiving.damageEntity(EntityLiving.java:644)
	at net.minecraft.server.v1_6_R3.EntityMonster.damageEntity(EntityMonster.java:39)
	at net.minecraft.server.v1_6_R3.EntityZombie.damageEntity(EntityZombie.java:127)
	at net.minecraft.server.v1_6_R3.EntityHuman.attack(EntityHuman.java:889)
	at net.minecraft.server.v1_6_R3.PlayerConnection.a(PlayerConnection.java:1158)
	at net.minecraft.server.v1_6_R3.Packet7UseEntity.handle(SourceFile:36)
	at org.spigotmc.netty.NettyNetworkManager.b(NettyNetworkManager.java:230)
	at net.minecraft.server.v1_6_R3.PlayerConnection.e(PlayerConnection.java:117)
	at net.minecraft.server.v1_6_R3.ServerConnection.b(SourceFile:37)
	at org.spigotmc.netty.NettyServerConnection.b(NettyServerConnection.java:132)
	at net.minecraft.server.v1_6_R3.MinecraftServer.t(MinecraftServer.java:594)
	at net.minecraft.server.v1_6_R3.DedicatedServer.t(DedicatedServer.java:240)
	at net.minecraft.server.v1_6_R3.MinecraftServer.s(MinecraftServer.java:483)
	at net.minecraft.server.v1_6_R3.MinecraftServer.run(MinecraftServer.java:415)
	at net.minecraft.server.v1_6_R3.ThreadServerApplication.run(SourceFile:583)
Caused by: java.lang.StringIndexOutOfBoundsException: String index out of range: -5
	at java.lang.String.charAt(Unknown Source)
	at maincode.LeveledMobs.setName(LeveledMobs.java:231)
	at maincode.LeveledMobs.EntityDamageEvent(LeveledMobs.java:207)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:425)
	... 22 more