15:07:51 [SEVERE] Could not pass event EntityDamageByEntityEvent to WallsPlugin v0.5.6
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:30)
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:478)
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:463)
        at org.bukkit.craftbukkit.v1_6_R2.event.CraftEventFactory.callEvent(CraftEventFactory.java:94)
        at org.bukkit.craftbukkit.v1_6_R2.event.CraftEventFactory.callEntityDamageEvent(CraftEventFactory.java:398)
        at org.bukkit.craftbukkit.v1_6_R2.event.CraftEventFactory.handleEntityDamageEvent(CraftEventFactory.java:423)
        at net.minecraft.server.v1_6_R2.EntityLiving.damageEntity(EntityLiving.java:643)
        at net.minecraft.server.v1_6_R2.EntityHuman.damageEntity(EntityHuman.java:715)
        at net.minecraft.server.v1_6_R2.EntityPlayer.damageEntity(EntityPlayer.java:394)
        at net.minecraft.server.v1_6_R2.EntityHuman.attack(EntityHuman.java:885)
        at net.minecraft.server.v1_6_R2.PlayerConnection.a(PlayerConnection.java:1148)
        at net.minecraft.server.v1_6_R2.Packet7UseEntity.handle(SourceFile:36)
        at org.spigotmc.netty.NettyNetworkManager.b(NettyNetworkManager.java:230)
        at net.minecraft.server.v1_6_R2.PlayerConnection.e(PlayerConnection.java:116)
        at net.minecraft.server.v1_6_R2.ServerConnection.b(SourceFile:37)
        at org.spigotmc.netty.NettyServerConnection.b(NettyServerConnection.java:125)
        at net.minecraft.server.v1_6_R2.MinecraftServer.t(MinecraftServer.java:592)
        at net.minecraft.server.v1_6_R2.DedicatedServer.t(DedicatedServer.java:239)
        at net.minecraft.server.v1_6_R2.MinecraftServer.s(MinecraftServer.java:481)
        at net.minecraft.server.v1_6_R2.MinecraftServer.run(MinecraftServer.java:413)
        at net.minecraft.server.v1_6_R2.ThreadServerApplication.run(SourceFile:582)
Caused by: java.lang.NullPointerException
        at oneric.bukkit.walls.events.PlayerEvents.onPlayerDie(PlayerEvents.java:98)
        at sun.reflect.GeneratedMethodAccessor118.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:425)
        ... 22 more