Bukkit

What steps will reproduce the problem?
1. Enabling the zombie spawning part of the plugin and starting up the server (for the second error)
2. When someone dies (for the first error)

What is the expected output? What do you see instead?

Well, I hope I can fix this problem so it doesn't lag and/or spam my server console. Also I really want to make my server fully functional.

What version of the product are you using?

BackFromTheDead v0.9.4.8

Do you have an error log of what happened?

2013-04-19 20:50:35 [SEVERE] Could not pass event EntityDeathEvent to BackFromTheDead v0.9.4.8
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.SimplePluginManager.fireEvent(SimplePluginManager.java:477)
    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:462)
    at org.bukkit.craftbukkit.v1_5_R2.event.CraftEventFactory.callEntityDeathEvent(CraftEventFactory.java:322)
    at net.minecraft.server.v1_5_R2.EntityLiving.dropDeathLoot(EntityLiving.java:945)
    at net.minecraft.server.v1_5_R2.EntityLiving.die(EntityLiving.java:893)
    at net.minecraft.server.v1_5_R2.EntityLiving.damageEntity(EntityLiving.java:750)
    at net.minecraft.server.v1_5_R2.EntityMonster.damageEntity(EntityMonster.java:39)
    at net.minecraft.server.v1_5_R2.EntityLiving.a(EntityLiving.java:978)
    at net.minecraft.server.v1_5_R2.Entity.a(Entity.java:772)
    at net.minecraft.server.v1_5_R2.EntityLiving.a(EntityLiving.java:243)
    at net.minecraft.server.v1_5_R2.Entity.move(Entity.java:619)
    at net.minecraft.server.v1_5_R2.EntityLiving.e(EntityLiving.java:1083)
    at net.minecraft.server.v1_5_R2.EntityLiving.c(EntityLiving.java:1332)
    at net.minecraft.server.v1_5_R2.EntityMonster.c(EntityMonster.java:20)
    at net.minecraft.server.v1_5_R2.EntityZombie.c(EntityZombie.java:116)
    at net.minecraft.server.v1_5_R2.EntityLiving.l_(EntityLiving.java:526)
    at net.minecraft.server.v1_5_R2.EntityMonster.l_(EntityMonster.java:24)
    at net.minecraft.server.v1_5_R2.EntityZombie.l_(EntityZombie.java:135)
    at net.minecraft.server.v1_5_R2.World.entityJoinedWorld(World.java:1355)
    at net.minecraft.server.v1_5_R2.WorldServer.entityJoinedWorld(WorldServer.java:614)
    at net.minecraft.server.v1_5_R2.World.playerJoinedWorld(World.java:1336)
    at net.minecraft.server.v1_5_R2.World.tickEntities(World.java:1224)
    at net.minecraft.server.v1_5_R2.WorldServer.tickEntities(WorldServer.java:480)
    at net.minecraft.server.v1_5_R2.MinecraftServer.r(MinecraftServer.java:562)
    at net.minecraft.server.v1_5_R2.DedicatedServer.r(DedicatedServer.java:225)
    at net.minecraft.server.v1_5_R2.MinecraftServer.q(MinecraftServer.java:476)
    at net.minecraft.server.v1_5_R2.MinecraftServer.run(MinecraftServer.java:409)
    at net.minecraft.server.v1_5_R2.ThreadServerApplication.run(SourceFile:573)
Caused by: java.lang.IllegalArgumentException: Cannot drop a Null item.
    at org.apache.commons.lang.Validate.notNull(Validate.java:203)
    at org.bukkit.craftbukkit.v1_5_R2.CraftWorld.dropItem(CraftWorld.java:295)
    at org.bukkit.craftbukkit.v1_5_R2.CraftWorld.dropItemNaturally(CraftWorld.java:313)
    at me.apollo.backfromthedead.backfromthedeadcore.CoreListener.onEntityDeath(CoreListener.java:399)
    at sun.reflect.GeneratedMethodAccessor122.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)
    ... 29 more

2013-04-18 20:30:40 [SEVERE] Could not pass event CreatureSpawnEvent to BackFromTheDead v0.9.4.8
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.SimplePluginManager.fireEvent(SimplePluginManager.java:477)
    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:462)
    at org.bukkit.craftbukkit.v1_5_R2.event.CraftEventFactory.callCreatureSpawnEvent(CraftEventFactory.java:234)
    at net.minecraft.server.v1_5_R2.World.addEntity(World.java:924)
    at net.minecraft.server.v1_5_R2.SpawnerCreature.spawnEntities(SpawnerCreature.java:159)
    at net.minecraft.server.v1_5_R2.WorldServer.doTick(WorldServer.java:186)
    at net.minecraft.server.v1_5_R2.MinecraftServer.r(MinecraftServer.java:554)
    at net.minecraft.server.v1_5_R2.DedicatedServer.r(DedicatedServer.java:225)
    at net.minecraft.server.v1_5_R2.MinecraftServer.q(MinecraftServer.java:476)
    at net.minecraft.server.v1_5_R2.MinecraftServer.run(MinecraftServer.java:409)
    at net.minecraft.server.v1_5_R2.ThreadServerApplication.run(SourceFile:573)
Caused by: java.lang.IllegalArgumentException: n must be positive
    at java.util.Random.nextInt(Unknown Source)
    at me.apollo.backfromthedead.backfromthedeadzombiecontrol.ZombieController.getEntityToSpawn(ZombieController.java:492)
    at me.apollo.backfromthedead.backfromthedeadzombiecontrol.ZombieController.doSpawnCode(ZombieController.java:215)
    at me.apollo.backfromthedead.backfromthedeadzombiecontrol.ZombieController.onZombieSpawn(ZombieController.java:203)
    at sun.reflect.GeneratedMethodAccessor35.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)
    ... 12 more

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