Bukkit

What steps will reproduce the problem?

1. Left-Click on the Global-Shop-Sign (Buy from the Server)

What is the expected output? What do you see instead?

Nothing happens if I left-click on the sign. Only the roor-message appears in the log

What version of the product are you using?

2.0

Do you have an error log of what happened?

10:41:17 [SEVERE] Could not pass event PlayerInteractEvent to DynamicShop v2.0
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_6_R2.event.CraftEventFactory.callPlayerInte
ractEvent(CraftEventFactory.java:190)
        at net.minecraft.server.v1_6_R2.PlayerInteractManager.dig(PlayerInteract
Manager.java:108)
        at net.minecraft.server.v1_6_R2.PlayerConnection.a(PlayerConnection.java
:538)
        at net.minecraft.server.v1_6_R2.Packet14BlockDig.handle(SourceFile:46)
        at net.minecraft.server.v1_6_R2.NetworkManager.b(NetworkManager.java:296
)
        at net.minecraft.server.v1_6_R2.PlayerConnection.e(PlayerConnection.java
:116)
        at net.minecraft.server.v1_6_R2.ServerConnection.b(SourceFile:37)
        at net.minecraft.server.v1_6_R2.DedicatedServerConnection.b(SourceFile:3
0)
        at net.minecraft.server.v1_6_R2.MinecraftServer.t(MinecraftServer.java:5
90)
        at net.minecraft.server.v1_6_R2.DedicatedServer.t(DedicatedServer.java:2
26)
        at net.minecraft.server.v1_6_R2.MinecraftServer.s(MinecraftServer.java:4
86)
        at net.minecraft.server.v1_6_R2.MinecraftServer.run(MinecraftServer.java
:419)
        at net.minecraft.server.v1_6_R2.ThreadServerApplication.run(SourceFile:5
82)
Caused by: java.lang.NullPointerException
        at me.zylinder.dynamicshop.PlayerHandler.checkInventory(PlayerHandler.ja
va:137)
        at me.zylinder.dynamicshop.TransactionHandler.buyGlobal(TransactionHandl
er.java:85)
        at me.zylinder.dynamicshop.SignHandler.leftClickGlobal(SignHandler.java:
186)
        at me.zylinder.dynamicshop.DynamicShopPlayerListener.onPlayerInteract(Dy
namicShopPlayerListener.java:59)
        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
>

Please provide any additional information below.