What does this error mean? How do I solve it?

Code:

17:06:57 [SEVERE] Could not pass event EntityDamageByEntityEvent to GalessServer
v1.0
org.bukkit.event.EventException
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.ja
va:427)
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.jav
a:62)
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.j
ava:477)
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.j
ava:462)
        at net.minecraft.server.v1_5_R3.Explosion.a(Explosion.java:167)
        at net.minecraft.server.v1_5_R3.World.createExplosion(World.java:1631)
        at net.minecraft.server.v1_5_R3.WorldServer.createExplosion(WorldServer.
java:844)
        at net.minecraft.server.v1_5_R3.EntityTNTPrimed.explode(EntityTNTPrimed.
java:83)
        at net.minecraft.server.v1_5_R3.EntityTNTPrimed.l_(EntityTNTPrimed.java:
63)
        at net.minecraft.server.v1_5_R3.World.entityJoinedWorld(World.java:1355)
 
        at net.minecraft.server.v1_5_R3.WorldServer.entityJoinedWorld(WorldServe
r.java:614)
        at net.minecraft.server.v1_5_R3.World.playerJoinedWorld(World.java:1336)
 
        at net.minecraft.server.v1_5_R3.World.tickEntities(World.java:1224)
        at net.minecraft.server.v1_5_R3.WorldServer.tickEntities(WorldServer.jav
a:480)
        at net.minecraft.server.v1_5_R3.MinecraftServer.r(MinecraftServer.java:5
63)
        at net.minecraft.server.v1_5_R3.DedicatedServer.r(DedicatedServer.java:2
26)
        at net.minecraft.server.v1_5_R3.MinecraftServer.q(MinecraftServer.java:4
77)
        at net.minecraft.server.v1_5_R3.MinecraftServer.run(MinecraftServer.java
:410)
        at net.minecraft.server.v1_5_R3.ThreadServerApplication.run(SourceFile:5
73)
Caused by: java.lang.NullPointerException

I have been coding for a while, but I don't know what this really means is happening other than the obvious NullPointer. I don't see where the pointer is being encountered. The error happens seemingly randomly when players are triggering the event. The console is spammed for about 1 minute before resuming normal play. During the time the error is spammed, players cannot chat/interact/etc as if the server were crashing.

 

Is there more on the console after the NPE? The lines that follow it should clearly state which lines the errors are coming from. If you were to post the code causing the error, we could possibly help you figure it out.

 

You cut off some of the error. Below the "Caused by: java.lang.NullPointerException", what does it say? It gives you a line in your code where a value is null.

EDIT: Ninja'd by stealth2800