Attempt to compare nil with number?

I run my game and when I go into the scene with the code displayed below I wait a little and then it says (attempt to compare nil with number)

<code>

        local function scrolltile(self,event)

            if self.x < -320 then

                self.x = 320

            else

                self.x = self.x - self.speed

            end

        end    

        

        tileback.enterFrame = scrolltile

        Runtime:addEventListener(“enterFrame”, tileback)

        

        tileback1.enterFrame = scrolltile

        Runtime:addEventListener(“enterFrame”, tileback1)

<code>

Thanks a ton!

Please only ask your question once.

Any one wanting to respond, please do so here:  http://forums.coronalabs.com/topic/43888-attempt-to-compare-nil-with-number/

Thanks

Rob

Please only ask your question once.

Any one wanting to respond, please do so here:  http://forums.coronalabs.com/topic/43888-attempt-to-compare-nil-with-number/

Thanks

Rob