NPC.lua And Npchandler.lua crashing server

[Lightonia]

Hey, there is some dude that found an exploit that makes my server crash all the time for some reason. I dont know why but it is the NPCs for sure;

npc.lua

function selfSayChannel(cid, message)
   return selfSay(message, cid, false)
end

function selfMoveToThing(id)
   errors(false)
   local thing = getThing(id)

   errors(true)
   if(thing.uid == 0) then
     return
   end

   local t = getThingPosition(id)
   selfMoveTo(t.x, t.y, t.z)
   return
end

function selfMoveTo(x, y, z)
   local position = {x = 0, y = 0, z = 0}
   if(type(x) ~= "table") then
     position = Position(x, y, z)
   else
     position = x
   end

   if(isValidPosition(position)) then
     doSteerCreature(getNpcId(), position)
   end
end

function selfMove(direction, flags)
   local flags = flags or 0
   doMoveCreature(getNpcId(), direction, flags)
end

function selfTurn(direction)
   doCreatureSetLookDirection(getNpcId(), direction)
end

function getNpcDistanceTo(id)
   errors(false)
   local thing = getThing(id)

   errors(true)
   if(thing.uid == 0) then
     return nil
   end

   local c = getCreaturePosition(id)
   if(not isValidPosition(c)) then
     return nil
   end

   local s = getCreaturePosition(getNpcId())
   if(not isValidPosition(s) or s.z ~= c.z) then
     return nil
   end

   return math.max(math.abs(s.x - c.x), math.abs(s.y - c.y))
end

function doMessageCheck(message, keyword)
   if(type(keyword) == "table") then
     return table.isStrIn(keyword, message)
   end

   local a, b = message:lower():find(keyword:lower())
   if(a ~= nil and b ~= nil) then
     return true
   end

   return false
end

function doNpcSellItem(cid, itemid, amount, subType, ignoreCap, inBackpacks, backpack)
   local amount, subType, ignoreCap, item = amount or 1, subType or 1, ignoreCap and true or false, 0
   if(isItemStackable(itemid)) then
     if(isItemRune(itemid)) then
       amount = amount * subType
     end

     local count = amount
     repeat
       item = doCreateItemEx(itemid, math.min(100, count))
       if(doPlayerAddItemEx(cid, item, ignoreCap) ~= RETURNVALUE_NOERROR) then
         return 0, 0
       end

       count = count - math.min(100, count)
     until count == 0
     return amount, 0
   end

   local a = 0
   if(inBackpacks) then
     local container, b = doCreateItemEx(backpack, 1), 1
     for i = 1, amount do
       item = doAddContainerItem(container, itemid, subType)
       if(itemid == ITEM_PARCEL) then
         doAddContainerItem(item, ITEM_LABEL)
       end

       if(isInArray({(getContainerCapById(backpack) * b), amount}, i)) then
         if(doPlayerAddItemEx(cid, container, ignoreCap) ~= RETURNVALUE_NOERROR) then
           b = b - 1
           break
         end

         a = i
         if(amount > i) then
           container = doCreateItemEx(backpack, 1)
           b = b + 1
         end
       end
     end

     return a, b
   end

   for i = 1, amount do
     item = doCreateItemEx(itemid, subType)
     if(itemid == ITEM_PARCEL) then
       doAddContainerItem(item, ITEM_LABEL)
     end

     if(doPlayerAddItemEx(cid, item, ignoreCap) ~= RETURNVALUE_NOERROR) then
       break
     end

     a = i
   end

   return a, 0
end

function doRemoveItemIdFromPosition(id, n, position)
   local thing = getThingFromPos({x = position.x, y = position.y, z = position.z, stackpos = 1})
   if(thing.itemid ~= id) then
     return false
   end

   doRemoveItem(thing.uid, n)
   return true
end

function getNpcName()
   return getCreatureName(getNpcId())
end

function getNpcPos()
   return getThingPosition(getNpcId())
end

function selfGetPosition()
   local t = getThingPosition(getNpcId())
   return t.x, t.y, t.z
end

msgcontains = doMessageCheck
moveToPosition = selfMoveTo
moveToCreature = selfMoveToThing
selfMoveToCreature = selfMoveToThing
selfMoveToPosition = selfMoveTo
isPlayerPremiumCallback = isPremium
doPosRemoveItem = doRemoveItemIdFromPosition
doRemoveItemIdFromPos = doRemoveItemIdFromPosition
doNpcBuyItem = doPlayerRemoveItem
doNpcSetCreatureFocus = selfFocus
getNpcCid = getNpcId
getDistanceTo = getNpcDistanceTo
getDistanceToCreature = getNpcDistanceTo
getNpcDistanceToCreature = getNpcDistanceTo

and npchandler.lua
http://pastebin.com/xB8QE7ev