19:35:12 [SEVERE] Could not pass event EntityDeathEvent to EntityManager
org.bukkit.event.EventException
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:304)
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:465)
        at org.bukkit.craftbukkit.event.CraftEventFactory.callEntityDeathEvent(CraftEventFactory.java:299)
        at net.minecraft.server.EntitySpider.dropDeathLoot(EntitySpider.java:136)
        at net.minecraft.server.EntityLiving.die(EntityLiving.java:781)
        at net.minecraft.server.EntityLiving.damageEntity(EntityLiving.java:677)
        at net.minecraft.server.EntityMonster.damageEntity(EntityMonster.java:38)
        at net.minecraft.server.EntityHuman.attack(EntityHuman.java:793)
        at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:1019)
        at net.minecraft.server.Packet7UseEntity.handle(SourceFile:33)
        at net.minecraft.server.NetworkManager.b(NetworkManager.java:234)
        at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:118)
        at net.minecraft.server.NetworkListenThread.a(NetworkListenThread.java:78)
        at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:576)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:465)
        at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)
Caused by: java.lang.NullPointerException
        at net.milkycraft.listeners.ExpListener.onTaggedMobDeath(ExpListener.java:51)
        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:302)
        ... 16 more