I follow Chalacade's turtorial for this code, if possible please point out the wrong part and rewrite it. Thank you

the ERROR: Error Resources/anim8.lua:36: frameWidth should be a number, was "nil" Traceback [love "callbacks.lua"]:228: in function 'handler' [C]: in function 'error' Resources/anim8.lua:36: in function 'assertPositiveInteger' Resources/anim8.lua:101: in function 'newGrid' main.l...