How to fix it (attempt to index a nil value)

[Adrenaline]

Hi all, i found nice script but dont work dont know how to fix it

The Forgotten Server 0.3.6 8.54 Debian6

[Error - Action Interface]
data/actions/scripts/other/quest.lua
Description:
attempt to index a nil value
[Warning - Event::loadScript] Cannot load script (data/actions/scripts/other/quest.lua)

Script:

local config = {
level = 25,
storageid = 65535,
itemid1 = 2177,
itemid2 = 2146,
itemid3 = 2229,
itemid4 = 7591,
}
item1 = getThingFromPos(i1)
item2 = getThingFromPos(i2)
item3 = getThingFromPos(i3)
item4 = getThingFromPos(i4)
i1 = {x=899, y=872, z=8, stackpos=2}
i2 = {x=903, y=877, z=8, stackpos=2}
i3 = {x=908, y=872, z=8, stackpos=2}
i4 = {x=903, y=868, z=8, stackpos=2}


function onUse(cid, item, fromPosition, itemEx, toPosition)
  if getPlayerLevel(cid) > config.level then
    if config.item1.uid == itemid1 then
      if config.item2.uid == itemid2 then
	if config.item3.uid == itemid3 then
	  if config.item4.uid == itemid4 then
	    if doRemoveItem(config.item1.uid) and doRemoveItem(config.item2.uid) and doRemoveItem(config.item3.uid) and doRemoveItem(config.item4.uid) == TRUE then
	      if setPlayerStorageValue(cid, config.storageid, 1) == TRUE then
		sendPlayerTextMessage(cid, TALKTYPE_ORANGE, "You can now continue your jurney.")
	      else
		sendPlayerTextMessage(cid, TALKTYPE_ORANGE, "Error, please contact an administrator (error code #2).")
	      end
	    else
	      sendPlayerTextMessage(cid, TALKTYPE_ORANGE, "Error, please contact an administrator (error code #1).")
	    end
	  else
	    sendPlayerTextMessage(cid, TALKTYPE_ORANGE, "Put the " .. getItemName(config.itemid1) .. " on the left place.")
	  end
	else
	  sendPlayerTextMessage(cid, TALKTYPE_ORANGE, "Put the " .. getItemName(config.itemid2) .. " on the bottom place.")
	end
      else
	sendPlayerTextMessage(cid, TALKTYPE_ORANGE, "Put the " .. getItemName(config.itemid3) .. " on the right place.")
      end
    else
      sendPlayerTextMessage(cid, TALKTYPE_ORANGE, "Put the " .. getItemName(config.itemid4) .. " on the top place.")
    end
  else
    sendPlayerTextMessage(cid, TALKTYPE_ORANGE, "You can't make this quest yet, you need level " .. config.level .. ", you are only level " .. getPlayerLevel(cid) .. ".")
  end
  return TRUE
end

Rep+ for help..