Oh, I'm sorry I misunderstood. If you haven't sent anything yet, then by all means fill out a new form. Use the new case number on all your material. I believe that on the online form, there is an area where you can "Add information" that you'd like the DOS to know. There, you can add a sentence like "Note: I previously filled out an online application that I later discovered contained errors. I did not submit the fee or any other materials to follow up on that application and consider this my actual application".
If you decide to write such a note (either with the application or as a footnote on your Statement of Reason), just emphasize that you did not pay the fee for the older one because the DOS will not actually open the case anyway without the fee so it will be clear to them that you only legally submitted one application. I am not even sure such a note is necessary because you did not send the fee. I'll leave that up to you. But either way, I think it is perfectly safe to fill out a new online form.