Bukkit

16:52:59 [SEVERE] Could not pass event InventoryClickEvent to MiningMachine v0.7.5
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.SimplePluginManager.fireEvent(SimplePluginManager.java:477)
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:462)
        at net.minecraft.server.v1_5_R3.PlayerConnection.a(PlayerConnection.java:1172)
        at net.minecraft.server.v1_5_R3.Packet102WindowClick.handle(SourceFile:31)
        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)
Caused by: java.lang.NullPointerException
        at com.pluggertech.miningmachine.MachineListener.inventoryClick(MachineListener.java:97)
        at sun.reflect.GeneratedMethodAccessor174.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)
        ... 14 more