OtherDrops Error

09:40 PM [SEVERE] Could not pass event EntityDeathEvent to OtherDrops v2.8b.542
Caused by: java.lang.NullPointerException
    at com.gmail.zariust.otherdrops.subject.EnvironmentAgent.matches(EnvironmentAgent.java:87)
    at com.gmail.zariust.otherdrops.event.CustomDrop.isTool(CustomDrop.java:226)
    at com.gmail.zariust.otherdrops.event.CustomDrop.matches(CustomDrop.java:111)
    at com.gmail.zariust.otherdrops.OtherDrops.gatherDrops(OtherDrops.java:478)
    at com.gmail.zariust.otherdrops.OtherDrops.performDrop(OtherDrops.java:266)
    at com.gmail.zariust.otherdrops.listener.OdEntityListener.onEntityDeath(OdEntityListener.java:86)
    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:425)
    at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
    at org.bukkit.plugin.TimedRegisteredListener.callEvent(TimedRegisteredListener.java:35)
    at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:477)
    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:462)
    at org.bukkit.craftbukkit.v1_5_R3.event.CraftEventFactory.callEntityDeathEvent(CraftEventFactory.java:323)
    at net.minecraft.server.v1_5_R3.EntityPig.dropDeathLoot(EntityPig.java:109)
    at net.minecraft.server.v1_5_R3.EntityLiving.die(EntityLiving.java:893)
    at net.minecraft.server.v1_5_R3.EntityLiving.damageEntity(EntityLiving.java:750)
    at net.minecraft.server.v1_5_R3.EntityAnimal.damageEntity(SourceFile:119)
    at net.minecraft.server.v1_5_R3.EntityHuman.attack(EntityHuman.java:874)
    at net.minecraft.server.v1_5_R3.PlayerConnection.a(PlayerConnection.java:1101)
    at net.minecraft.server.v1_5_R3.Packet7UseEntity.handle(SourceFile:36)
    at net.minecraft.server.v1_5_R3.NetworkManager.b(NetworkManager.java:292)
    at net.minecraft.server.v1_5_R3.PlayerConnection.d(PlayerConnection.java:109)
    at net.minecraft.server.v1_5_R3.ServerConnection.b(SourceFile:35)
    at net.minecraft.server.v1_5_R3.DedicatedServerConnection.b(SourceFile:30)
    at net.minecraft.server.v1_5_R3.MinecraftServer.r(MinecraftServer.java:581)
    at net.minecraft.server.v1_5_R3.DedicatedServer.r(DedicatedServer.java:226)
    at net.minecraft.server.v1_5_R3.MinecraftServer.q(MinecraftServer.java:477)
    at net.minecraft.server.v1_5_R3.MinecraftServer.run(MinecraftServer.java:410)
    at net.minecraft.server.v1_5_R3.ThreadServerApplication.run(SourceFile:573)