Need Some Npc Help Red Skull and black skull check

[Angel Of Death]

it doesnt work
the npc doesnt respond at all you say hi and he keeps walking around

local keywordHandler = KeywordHandler:new()
local npcHandler = NpcHandler:new(keywordHandler)
NpcSystem.parseParameters(npcHandler)
 
local storage = getPlayerStorageValue(cid, 60055)
 
function onCreatureAppear(cid)
	npcHandler:onCreatureAppear(cid)
end
function onCreatureDisappear(cid)
	npcHandler:onCreatureDisappear(cid)
end
function onCreatureSay(cid, type, msg)
	npcHandler:onCreatureSay(cid, type, msg)
end
function onThink()
	npcHandler:onThink()
end
 
npcHandler:setMessage(MESSAGE_GREET, "Greetings |PLAYERNAME|.")
 
function creatureSayCallback(cid, type, msg, item, fromPosition, itemEx, toPosition, uid)
	if(not npcHandler:isFocused(cid)) then
		return false
	end
	local talkUser = NPCHANDLER_CONVBEHAVIOR == CONVERSATION_DEFAULT and 0 or cid
 
 
	if(msgcontains(msg, "Join")) then
		if getPlayerSkullType(cid) =< 4 then
		npcHandler:say( "Welcome", cid, 1000)
	else
		npcHandler:say( "What Are you Talking About!!!!" , cid, 1000)
	end
 
	elseif msgcontains(msg, "yes") then
		if getPlayerSkullType(cid) =< 4 then
		--Do Script Functions
	else
		npcHandler:say("I Havent Said AnyThing For You To Say Yes Too!!!", cid, 1000)
	end	
	return true
end
end
 
npcHandler:setCallback(CALLBACK_MESSAGE_DEFAULT, creatureSayCallback)
npcHandler:addModule(FocusModule:new())

[Error - Npc interface]
data/npc/scripts/Dark BrotherHood.lua:onCreatureSay
Description:
data/npc/scripts/Dark BrotherHood.lua:17: attempt to call method 'getPlayerSkull
' (a nil value)
stack traceback:
        data/npc/scripts/Dark BrotherHood.lua:17: in function 'getPlayerSkull'
        data/npc/scripts/Dark BrotherHood.lua:32: in function 'callback'
        data/npc/lib/npcsystem/npchandler.lua:383: in function 'onCreatureSay'
        data/npc/scripts/Dark BrotherHood.lua:14: in function <data/npc/scripts/
Dark BrotherHood.lua:13>