Cs, potřeboval bych poradit co tak přibližně znamená tato chyba moc jí nechápu

Zde: 2012-09-13 18:50:47 [SEVERE] Could not pass event SignChangeEvent to ChestShop
org.bukkit.event.EventException
at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:332)
at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:477)
at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:462)
at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:1299)
at net.minecraftserverhook.NetServerHandlerProxy.a(NetServerHandlerProxy.java:214)
at net.minecraft.server.Packet130UpdateSign.handle(SourceFile:46)
at net.minecraft.server.NetworkManager.b(NetworkManager.java:276)
at net.minecraft.server.NetServerHandler.d(NetServerHandler.java:109)
at net.minecraft.server.ServerConnection.b(SourceFile:35)
at net.minecraft.server.DedicatedServerConnection.b(SourceFile:30)
at net.minecraft.server.MinecraftServer.q(MinecraftServer.java:578)
at net.minecraft.server.DedicatedServer.q(DedicatedServer.java:213)
at net.minecraft.server.MinecraftServer.p(MinecraftServer.java:474)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:406)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:539)
Caused by: java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Long.parseLong(Long.java:453)
at com.Acrobot.Breeze.Utils.MaterialUtil$Enchantment.getEnchantments(MaterialUtil.java:246)
at com.Acrobot.Breeze.Utils.MaterialUtil.getEnchantments(MaterialUtil.java:229)
at com.Acrobot.Breeze.Utils.MaterialUtil.getItem(MaterialUtil.java:182)
at com.Acrobot.ChestShop.Listeners.Block.SignChange.onSignChange(SignChange.java:43)
at sun.reflect.GeneratedMethodAccessor334.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:330)
... 15 more