Custom spell self nil error.

[Ziore]

TFS 1.3 + OTC 8
I wanted to make a spell that has a chance to hit when it fires and when it returns it should hit everything in range, but for some reason i get a self nill error.

data/events/scripts/creature.lua:Creature@onTargetCombat
data/events/scripts/creature.lua:26: attempt to index local 'self' (a nil value)
stack traceback:
[C]: in function '__index'
data/events/scripts/creature.lua:26: in function <data/events/scripts/creature.lua:22>
[C]: in function 'doCombat'
data/spells/scripts/ziore/pool_of_blood.lua:54: in function <data/spells/scripts/ziore/pool_of_blood.lua:53>

local preRandomCombat, returningdmgCombat, combat = createCombatObject(), createCombatObject(), createCombatObject()
setCombatParam(combat, COMBAT_PARAM_EFFECT, CONST_ME_BLOODYSTEPS)
setCombatParam(combat, COMBAT_PARAM_TYPE, COMBAT_PHYSICALDAMAGE)
setCombatParam(returningdmgCombat, COMBAT_PARAM_EFFECT, CONST_ME_DRAWBLOOD)
setCombatParam(returningdmgCombat, COMBAT_PARAM_TYPE, COMBAT_DEATHDAMAGE)
local arr1 = {
    -- size
    {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
    {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
    {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
    {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
    {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
    {1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1},
    {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
    {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
    {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
    {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
    {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}
}
setCombatArea(preRandomCombat, createCombatArea(arr1))
setCombatArea(returningdmgCombat, createCombatArea(arr1))
function onTargetTileRandom(cid, pos)
    return math.random(2) == 1 and doCombat(cid, combat, positionToVariant(pos))
end
function onTargetTileReal(cid, pos)
    if math.random() == 0 then
        return false
    end
    local player = Player(cid)
    if not player then
        return false
    end
    local playerID = player:getId()
    player:getPosition():sendDistanceEffect(pos, CONST_ANI_EXPLOSION)
    addEvent(returnBlood, 1300, playerID, pos)
    return math.random(2) == 1 and doCombat(cid, combat, positionToVariant(pos))
end
function returnBlood(cid, pos)
    local player = Player(cid)
    pos:sendDistanceEffect(player:getPosition(), CONST_ANI_EXPLOSION)
end
function doReturningDamage(c, cid, var)
    doCombat(cid, c, var)
end
function onGetFormulaValues(player, skill, attack, factor)
    return (10) * -1, (20) * -1
end
setCombatCallback(preRandomCombat, CALLBACK_PARAM_TARGETTILE, 'onTargetTileRandom')
setCombatCallback(combat, CALLBACK_PARAM_TARGETTILE, 'onTargetTileReal')
setCombatCallback(combat, CALLBACK_PARAM_SKILLVALUE, 'onGetFormulaValues')
setCombatCallback(returningdmgCombat, CALLBACK_PARAM_SKILLVALUE, 'onGetFormulaValues')
function onCastSpell(cid, var)
    local player = Player(cid)
    if not player then
        return false
    end
    local playerID = player.getId()
    doCombat(cid, preRandomCombat, var)
    addEvent(doReturningDamage, 1000, returningdmgCombat, playerID, var)
    return true
end

Any ideas how to fix this would be lovely.
Regards, Ziore