If you want to make a button icon not fade when no item is selected, perhaps when you use a menu button with a dropdown items that do not require a selection, add !@disablenosel to the top of the function.
Did you try running the button? 
!@disablenosel won't do anything other than add a line with an unrecognised command, which causes an error when you run the button. Modifiers start with @ not with !.
Try adding @enableif:=true instead, although it seems a bad idea to me (outside a few special cases) as commands which automatically disable when nothing is selected do so because they won't work with nothing selected.
While in Customize mode, right-click a Button-Menu for a menu which includes the option to always enable the menu part.