Bukkit

This happens when I try to add inventory or remove.

[10:34:27 ERROR]: Could not pass event InventoryCloseEvent to MCPacks v3.6
org.bukkit.event.EventException
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.ja
va:320) ~[craftbukkit.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.jav
a:62) ~[craftbukkit.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.j
ava:486) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.j
ava:471) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
        at org.bukkit.craftbukkit.v1_7_R1.event.CraftEventFactory.handleInventor
yCloseEvent(CraftEventFactory.java:701) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-b
3020jnks]
        at net.minecraft.server.v1_7_R1.PlayerConnection.a(PlayerConnection.java
:1154) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
        at net.minecraft.server.v1_7_R1.PacketPlayInCloseWindow.a(PacketPlayInCl
oseWindow.java:15) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
        at net.minecraft.server.v1_7_R1.PacketPlayInCloseWindow.handle(PacketPla
yInCloseWindow.java:27) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
        at net.minecraft.server.v1_7_R1.NetworkManager.a(NetworkManager.java:146
) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
        at net.minecraft.server.v1_7_R1.ServerConnection.c(SourceFile:134) [craf
tbukkit.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
        at net.minecraft.server.v1_7_R1.MinecraftServer.u(MinecraftServer.java:6
55) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
        at net.minecraft.server.v1_7_R1.DedicatedServer.u(DedicatedServer.java:2
50) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
        at net.minecraft.server.v1_7_R1.MinecraftServer.t(MinecraftServer.java:5
45) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
        at net.minecraft.server.v1_7_R1.MinecraftServer.run(MinecraftServer.java
:457) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
        at net.minecraft.server.v1_7_R1.ThreadServerApplication.run(SourceFile:6
17) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
Caused by: java.lang.IllegalArgumentException: Path cannot be null
        at org.apache.commons.lang.Validate.notNull(Validate.java:203) ~[craftbu
kkit.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
        at org.bukkit.configuration.MemorySection.getDefault(MemorySection.java:
701) ~[craftbukkit.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
        at org.bukkit.configuration.MemorySection.get(MemorySection.java:198) ~[
craftbukkit.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
        at org.bukkit.configuration.MemorySection.contains(MemorySection.java:10
6) ~[craftbukkit.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
        at com.rb2750.backpack.EventHandle.onClose(EventHandle.java:48) ~[?:?]
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.7.0
]
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:1.7.0
]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1
.7.0]
        at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.7.0]
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.ja
va:318) ~[craftbukkit.jar:git-Bukkit-1.7.2-R0.3-b3020jnks]
        ... 14 more
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