Error that appears

23:24:43 [SEVERE] Could not pass event PlayerInteractEvent to NeilnetScavenge 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 org.bukkit.craftbukkit.v1_5_R2.event.CraftEventFactory.callPlayerInte
ractEvent(CraftEventFactory.java:181)
        at org.bukkit.craftbukkit.v1_5_R2.event.CraftEventFactory.callPlayerInte
ractEvent(CraftEventFactory.java:151)
        at net.minecraft.server.v1_5_R2.PlayerConnection.a(PlayerConnection.java
:1006)
        at net.minecraft.server.v1_5_R2.Packet18ArmAnimation.handle(SourceFile:4
1)
        at net.minecraft.server.v1_5_R2.NetworkManager.b(NetworkManager.java:292
)
        at net.minecraft.server.v1_5_R2.PlayerConnection.d(PlayerConnection.java
:113)
        at net.minecraft.server.v1_5_R2.ServerConnection.b(SourceFile:35)
        at net.minecraft.server.v1_5_R2.DedicatedServerConnection.b(SourceFile:3
0)
        at net.minecraft.server.v1_5_R2.MinecraftServer.r(MinecraftServer.java:5
80)
        at net.minecraft.server.v1_5_R2.DedicatedServer.r(DedicatedServer.java:2
25)
        at net.minecraft.server.v1_5_R2.MinecraftServer.q(MinecraftServer.java:4
76)
        at net.minecraft.server.v1_5_R2.MinecraftServer.run(MinecraftServer.java
:409)
        at net.minecraft.server.v1_5_R2.ThreadServerApplication.run(SourceFile:5
73)
Caused by: java.lang.NullPointerException
        at me.neilplugin.Scavenge.onPlayerInteract(Scavenge.java:37)
        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.ja
va:425)
        ... 16 more