Hi Steve,
There is not much I can add because your conclusions are correct. There is no abort action, so you have to check "if not empty".
I am assuming you don't like the "if not empty" idea because you create the script that works without conditions and then you wanted to add the if condition and you found it not ideal that you had to convert all script actions into conditional actions. What I usually to do, to structure scripts is to create two script buttons. The first one is your script without if, and the second one contains the IF and one conditional action which calls the 2nd script button (push <scriptbuttonid>). Finally, I hide the first button.
Cheers,
Tobias.