What to do about optional essay that does not apply to me?

I am applying to Carnegie Mellon, and one of the writing supplements asks for me to explain why I have taken a gap year, if I have taken one. The Common App won’t let me submit my writing supplements because it says I have not completed everything, but obviously I am not supposed to fill out that part. How do I bypass it?

Just say something like “I have not taken a gap year.”

Maybe try writing a one sentence essay, “I did not take a gap year.”