GetItemAttribute. Item not found. Help

[kermaxpl]

Hey guys, again me
I want to do spell which will do aoe every 3 player's autoattacks. I add this in actions.

function onUse(cid, item, fromPosition, itemEx, toPosition)
	if getPlayerVocation(cid) == 4 then
		if getCreatureStorage(cid, 99996) ~= 3 then
			doCreatureSetStorage(cid, 99996, getCreatureStorage(cid, 99996) + 1)
		else
			doCreatureSetStorage(cid, 99996, 0)
		end
	end
	return true
end

Then add this spell:

local combat = createCombatObject()
setCombatParam(combat, COMBAT_PARAM_EFFECT, CONST_ME_DRAWBLOOD)

local area = createCombatArea(AREA_SQUARE1X1)
setCombatArea(combat, area)

function onGetFormulaValues(param)
	local min = -(param.damage * 0.61)
	local max = -(param.damage * 0.75)
	return min, max
end

function thirdAA(param)
	if (getCreatureStorage(param.cid, 99996) == 3) then
		doCombat(param.cid, param.combat, param.var)
	end
end

setCombatCallback(combat, CALLBACK_PARAM_SKILLVALUE, "onGetFormulaValues")

function onCastSpell(cid, var)
     local weapon = getPlayerSlotItem(cid, CONST_SLOT_LEFT)
     local weapon2 = getPlayerSlotItem(cid, CONST_SLOT_RIGHT)
     local param = {}
     param.cid = cid
     param.var = var
     param.combat = combat
     if (getItemAttribute(weapon.uid, 'attack') == 0) then
    		param.damage = getItemAttribute(weapon2.uid, 'attack')
	else
    		param.damage = getItemAttribute(weapon.uid, 'attack')
     end  
	for i = 1, 40 do
		addEvent(thirdAA, i * 500, param)
	end
    return true 
end

Everything will be ok, but I have this and i don't know why:

[14:26:03.437] [Error - Spell Interface]
[14:26:03.437] data/spells/scripts/buffy/ThirdAA.lua:onCastSpell
[14:26:03.437] Description:
[14:26:03.437] (luaGetItemAttribute) Item not found

-- Edit
This doesn't work too:

getItemAttribute(getPlayerWeapon(cid, true).uid,  "attack")

--Edit2
ok, my mistake, wrong "if",
But now is is something wrong with onUse script. It don't change storage value

--Edit3
onUse changed to onUseWeapon and it works