nbt error

2012-11-07 15:58:58 [WARNING] [Shopkeepers] Failed to spawn shopkeeper at Larkspur,-7,51,-17
2012-11-07 15:58:58 [SEVERE] null
org.bukkit.command.CommandException: Unhandled exception executing command 'shopkeeper' in plugin Shopkeepers v1.8
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46)
	at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:185)
	at org.bukkit.craftbukkit.CraftServer.dispatchCommand(CraftServer.java:504)
	at net.minecraft.server.NetServerHandler.handleCommand(NetServerHandler.java:911)
	at net.minecraft.server.NetServerHandler.chat(NetServerHandler.java:824)
	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:806)
	at net.minecraft.server.Packet3Chat.handle(Packet3Chat.java:44)
	at net.minecraft.server.NetworkManager.b(NetworkManager.java:282)
	at net.minecraft.server.NetServerHandler.d(NetServerHandler.java:111)
	at net.minecraft.server.ServerConnection.b(SourceFile:35)
	at net.minecraft.server.DedicatedServerConnection.b(SourceFile:30)
	at net.minecraft.server.MinecraftServer.r(MinecraftServer.java:578)
	at net.minecraft.server.DedicatedServer.r(DedicatedServer.java:215)
	at net.minecraft.server.MinecraftServer.q(MinecraftServer.java:495)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:428)
	at net.minecraft.server.ThreadServerApplication.run(SourceFile:818)
Caused by: java.lang.NullPointerException
	at java.io.DataOutputStream.writeUTF(DataOutputStream.java:347)
	at java.io.DataOutputStream.writeUTF(DataOutputStream.java:323)
	at net.minecraft.server.NBTTagString.write(SourceFile:20)
	at net.minecraft.server.NBTTagList.write(SourceFile:26)
	at net.minecraft.server.NBTBase.a(SourceFile:112)
	at net.minecraft.server.NBTTagCompound.write(NBTTagCompound.java:29)
	at net.minecraft.server.NBTBase.a(SourceFile:112)
	at net.minecraft.server.NBTTagCompound.write(NBTTagCompound.java:29)
	at net.minecraft.server.NBTBase.a(SourceFile:112)
	at com.nisovin.shopkeepers.shoptypes.AdminShopkeeper.saveItemStack(AdminShopkeeper.java:328)
	at com.nisovin.shopkeepers.shoptypes.AdminShopkeeper.save(AdminShopkeeper.java:92)
	at com.nisovin.shopkeepers.ShopkeepersPlugin.saveReal(ShopkeepersPlugin.java:661)
	at com.nisovin.shopkeepers.ShopkeepersPlugin.save(ShopkeepersPlugin.java:649)
	at com.nisovin.shopkeepers.ShopkeepersPlugin.loadShopkeepersInChunk(ShopkeepersPlugin.java:582)
	at com.nisovin.shopkeepers.ShopkeepersPlugin.onEnable(ShopkeepersPlugin.java:102)
	at com.nisovin.shopkeepers.ShopkeepersPlugin.reload(ShopkeepersPlugin.java:228)
	at com.nisovin.shopkeepers.ShopkeepersPlugin.onCommand(ShopkeepersPlugin.java:235)
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44)
	... 15 more