Could not pass event CreatureSpawnEvent to NetherMobs
org.bukkit.event.EventException
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:341)
        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.event.CraftEventFactory.callCreatureSpawnEvent(CraftEventFactory.java:226)
        at net.minecraft.server.World.addEntity(World.java:841)
        at net.minecraft.server.BlockPumpkin.onPlace(BlockPumpkin.java:89)
        at org.getspout.spout.block.mcblock.CustomBlock.onPlace(CustomBlock.java:234)
        at net.minecraft.server.Chunk.a(Chunk.java:423)
        at net.minecraft.server.World.setRawTypeIdAndData(World.java:248)
        at net.minecraft.server.World.setRawTypeIdAndData(World.java:237)
        at net.minecraft.server.World.setTypeIdAndData(World.java:354)
        at net.minecraft.server.ItemBlock.interactWith(ItemBlock.java:85)
        at net.minecraft.server.ItemStack.placeItem(ItemStack.java:84)
        at net.minecraft.server.ItemInWorldManager.interact(ItemInWorldManager.java:371)
        at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:650)
        at net.minecraft.server.Packet15Place.handle(SourceFile:58)
        at net.minecraft.server.NetworkManager.b(NetworkManager.java:282)
        at net.minecraft.server.NetServerHandler.d(NetServerHandler.java:109)
        at org.getspout.spout.SpoutNetServerHandler.d(SpoutNetServerHandler.java:203)
        at net.minecraft.server.ServerConnection.b(SourceFile:35)
        at net.minecraft.server.DedicatedServerConnection.b(SourceFile:30)
        at net.minecraft.server.MinecraftServer.q(MinecraftServer.java:577)
        at net.minecraft.server.DedicatedServer.q(DedicatedServer.java:213)
        at net.minecraft.server.MinecraftServer.p(MinecraftServer.java:473)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:405)
        at net.minecraft.server.ThreadServerApplication.run(SourceFile:539)
Caused by: java.lang.NullPointerException
        at me.everdras.nethermobs.SpawnListener.onCreatureSpawn(SpawnListener.java:30)
        at sun.reflect.GeneratedMethodAccessor62.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:601)
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:339)
        ... 26 more