Error

2014-08-01 15:09:03 [SEVERE] Error occurred while enabling ServerShop-GUI v1.4.3 (Is it up to date?)
java.lang.NullPointerException
	at org.bukkit.inventory.ItemStack.<init>(ItemStack.java:94)
	at com.avalon.servershop.ServerShop.AddItemToShops(ServerShop.java:459)
	at com.avalon.servershop.ServerShop.createInventory(ServerShop.java:185)
	at com.avalon.servershop.ServerShop.onEnable(ServerShop.java:110)
	at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:217)
	at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:467)
	at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:383)
	at org.bukkit.craftbukkit.v1_6_R3.CraftServer.loadPlugin(CraftServer.java:279)
	at org.bukkit.craftbukkit.v1_6_R3.CraftServer.enablePlugins(CraftServer.java:261)
	at net.minecraft.server.MinecraftServer.func_71243_i(MinecraftServer.java:522)
	at net.minecraft.server.MinecraftServer.func_71222_d(MinecraftServer.java:486)
	at net.minecraft.server.MinecraftServer.func_71247_a(MinecraftServer.java:429)
	at net.minecraft.server.dedicated.DedicatedServer.func_71197_b(DedicatedServer.java:225)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:637)
	at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:583)