Bukkit

Getting this each time a user switches to something in the Quickbar.
It does not matter if the slot is empty or got an item.

2013-07-14 09:01:49 [SEVERE] Could not pass event PlayerItemHeldEvent to TokenShop v1.2
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 net.minecraft.server.v1_6_R2.PlayerConnection.a(PlayerConnection.java:757)
        at net.minecraft.server.v1_6_R2.Packet16BlockItemSwitch.handle(SourceFile:27)
        at org.spigotmc.netty.NettyNetworkManager.b(NettyNetworkManager.java:235)
        at net.minecraft.server.v1_6_R2.PlayerConnection.e(PlayerConnection.java:118)
        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 com.roguepanda.rptokens.TokenShop.itemSlotSwitch(TokenShop.java:371)
        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)
        ... 15 more

I also get this.