Charges potion

tengo un problema con una de mis scripts para recargar potion la escript recarga las potion y quita una cantidad x de dinero pero el problema sale cuanto el player poner los parametros del comando mal
ejemplo como se pone: !carga mana,1
ejemplo cuando sale el error !cargar mana


error el la linea 25
"if doPlayerRemoveMoney(cid, item.cost*amount) == LUA_NO_ERROR then"

data/talkactions/scripts/potions.lua:25: in function <data/talka
ctions/scripts/potions.lua:1>


function onSay(cid, words, param, channel)

local items =
{
['hp'] = {cost = 45, storage = 49989},
['mp'] = {cost = 50, storage = 49985},

['shp'] = {cost = 100, storage = 49988},
['smp'] = {cost = 80, storage = 49984},

['ghp'] = {cost = 190, storage = 49987},
['gmp'] = {cost = 120, storage = 49983}
}

local t = string.explode(param, ",")
local item = items[t[1]]
local amount = tonumber(t[2])

if getCreatureCondition(cid, CONDITION_INFIGHT) then
doPlayerSendTextMessage(cid, MESSAGE_STATUS_CONSOLE_BLUE, 'You cannot buy while you are fighting')
return true
end

if item then
if doPlayerRemoveMoney(cid, item.cost*amount) == LUA_NO_ERROR then
doPlayerSendTextMessage(cid, MESSAGE_STATUS_CONSOLE_BLUE, 'You have bought '..amount..' '..t[1]..' charges for '..(item.cost*amount)..' golden pieces.')
setPlayerStorageValue(cid, item.storage, getPlayerStorageValue(cid, item.storage)+amount)
else
doPlayerSendCancel(cid, 'You dont have enough money to buy that many charges.')
doSendMagicEffect(getPlayerPosition (cid), CONST_ME_POFF)
end
else
text = "Charges you can buy:\n"
for item1 in pairs (items) do
text = text .. "\n" .. item1
end
text = text .. "\n\nexample: type '!charges gmp,100' para comprar 100 gmp."
doPlayerPopupFYI(cid, text)
end
return true
end