Lua Error in console (GlobalEvents) antiEntrosaKillua

[sidekoolz]

[Error - GlobalEvent Interface]
data/globalevents/scripts/antiEntrosaKillua.luanThink
Description:
data/globalevents/scripts/antiEntrosaKillua.lua:8: attempt to compare nil with number
stack traceback:
data/globalevents/scripts/antiEntrosaKillua.lua:8: in function <data/globalevents/scripts/antiEntrosaKillua.lua:1>
[Error - GlobalEvents::think] Couldn't execute event: Anti Entrosa

<globalevent name="Anti Entrosa" interval="300000" script="antiEntrosaKillua.lua"/>

function onThink(interval, lastExecution, thinkInterval)
    local storages = {}
    for a,b in pairs(Entrosa.arenas) do
        storages[b.number] = b.storage
    end
    for x,y in pairs(storages) do
        local tab_sto = getGlobalTableStorage(y)
        if tonumber(tab_sto[4]) < os.time() then
            if tonumber(tab_sto[1]) <= os.time() then
                for _, pid in pairs(getPlayersOnline()) do
                    if getPlayerStorageValue(pid,Entrosa.sto) == x then
                        doPlayerSetStorageValue(pid,Entrosa.sto,-1)
                        doTeleportThing(pid,getTownTemplePosition(getPlayerTown(pid)))
                        doPlayerSendTextMessage(pid,MESSAGE_STATUS_CONSOLE_ORANGE,"A guerra entre as guilds acabou e você foi movido para o templo.")
                    end
                end
                local newTab = {}
                for l,t in next, tab_sto do
                    newTab[l] = 0
                end
                setGlobalTableStorage(y,newTab)
            end
        end
    end
    return true
end

Can someone help me? I'm using TFS Exclusive Edition 0.5 - Version Tibia 8.6