UI error :Attempt To Index a Nil Value

the error is in the line 2. it is an object reference, the reference exist but i dunno what to do
this is the screenshot, where is the error?

Your custom properties are set on the button, not the script
Change that or call GetCustomProperty() on BUTTON (script.parent)

thank you!! i actually came up with the solution right now, i realized that the script doesn't know where is the button.

i actually move my properties to the script, think is better