I’d just like to ask if the ECs are a required field, as in if you don’t fill out the slots the system wouldn’t accept your application?
You can submit it. But I bet there are interests that you have, things that you like to do that you could put in it. Are you an avid reader, are you creative in any crafts, do you like cooking, taking pictures ?
just write "None’ if you have none but your chances of admission at selective schools would be minimal.