NPC Shop - Help!

[Cosmotonio]

When i try to buy a item with trade window (NPC) i got this error:

[05/11/2008  17:12:15] Lua Script Error: [Npc interface] 
[05/11/2008  17:12:15] (Unknown scriptfile)

[05/11/2008  17:12:15] data/npc/lib/npcsystem/modules.lua:881: attempt to call global 'getPlayerMoney' (a nil value)
[05/11/2008  17:12:15] stack traceback:
[05/11/2008  17:12:15] 	data/npc/lib/npcsystem/modules.lua:881: in function 'callbackOnBuy'
[05/11/2008  17:12:15] 	data/npc/lib/npcsystem/npchandler.lua:251: in function 'processModuleCallback'
[05/11/2008  17:12:15] 	data/npc/lib/npcsystem/npchandler.lua:424: in function 'onBuy'
[05/11/2008  17:12:15] 	data/npc/lib/npcsystem/modules.lua:986: in function <data/npc/lib/npcsystem/modules.lua:986>

I use the npc lib from TFS 0.2.19