TFS 1.0 Playerdeath.lua - attempt to index a nil value

local deathListEnabled = true
local maxDeathRecords = 5

function onDeath(cid, corpse, killer, mostDamage, unjustified, mostDamage_unjustified)
    local player = Player(cid)

    player:sendTextMessage(MESSAGE_EVENT_ADVANCE, "You are dead.")
    if not deathListEnabled then
        return
    end

    local byPlayer = 0
    local killerCreature = Creature(killer)
    if killerCreature == nil then
        killerName = "field item"
    else
        if killerCreature:isPlayer() then
            byPlayer = 1
        else
            local master = killerCreature:getMaster()
            if master and master ~= killerCreature and master:isPlayer() then
                killerCreature = master
                byPlayer = 1
            end
        end
        killerName = killerCreature:getName()
    end

    local byPlayerMostDamage = 0
    if mostDamage == 0 then
        mostDamageName = "field item"
    else
        local mostDamageKiller = Creature(mostDamage)
        if mostDamageKiller:isPlayer() then
            byPlayerMostDamage = 1
        else
            local master = mostDamageKiller:getMaster()
            if master and master ~= mostDamageKiller and master:isPlayer() then
                mostDamageKiller = master
                byPlayerMostDamage = 1
            end
        end
        mostDamageName = mostDamageKiller:getName()
    end

    local playerGuid = player:getGuid()
    db.query("INSERT INTO `player_deaths` (`player_id`, `time`, `level`, `killed_by`, `is_player`, `mostdamage_by`, `mostdamage_is_player`, `unjustified`, `mostdamage_unjustified`) VALUES (" .. playerGuid .. ", " .. os.time() .. ", " .. player:getLevel() .. ", " .. db.escapeString(killerName) .. ", " .. byPlayer .. ", " .. db.escapeString(mostDamageName) .. ", " .. byPlayerMostDamage .. ", " .. unjustified .. ", " .. mostDamage_unjustified .. ")")
    local resultId = db.storeQuery("SELECT `player_id` FROM `player_deaths` WHERE `player_id` = " .. playerGuid)

    local deathRecords = 0
    local tmpResultId = resultId
    while tmpResultId ~= false do
        tmpResultId = result.next(resultId)
        deathRecords = deathRecords + 1
    end

    if resultId ~= false then
        result.free(resultId)
    end

    while deathRecords > maxDeathRecords do
        db.query("DELETE FROM `player_deaths` WHERE `player_id` = " .. playerGuid .. " ORDER BY `time` LIMIT 1")
        deathRecords = deathRecords - 1
    end

    if byPlayer == 1 then
        local guild = player:getGuild()
        local targetGuild = guild and guild:getId()
        if targetGuild ~= 0 then
            local killerGuild = killerCreature:getGuild():getId()
            if killerGuild ~= 0 and targetGuild ~= killerGuild and isInWar(cid, killerCreature) then
                local warId = false
                resultId = db.storeQuery("SELECT `id` FROM `guild_wars` WHERE `status` = 1 AND ((`guild1` = " .. killerGuild .. " AND `guild2` = " .. targetGuild .. ") OR (`guild1` = " .. targetGuild .. " AND `guild2` = " .. killerGuild .. "))")
                if resultId ~= false then
                    warId = result.getDataInt(resultId, "id")
                    result.free(resultId)
                end

                if warId ~= false then
                    db.query("INSERT INTO `guildwar_kills` (`killer`, `target`, `killerguild`, `targetguild`, `time`, `warid`) VALUES (" .. db.escapeString(killerName) .. ", " .. db.escapeString(player:getName()) .. ", " .. killerGuild .. ", " .. targetGuild .. ", " .. os.time() .. ", " .. warId .. ")")
                end
            end
        end
    end
end