I don't think it's a big deal if you can't come up with anything and leave it blank. They're not looking for another essay to read...especially if it's forced blabber. But here are some things to consider...
Tie yourself to the school. Make the personal connection. Your app and PS are beautiful, but they aren't catered to any specific school. Pretend for a moment that this is your #1 choice. Do you have any last words for them? Because they might be just that. If you applied to a massive number of schools or selected them superficially, this might take a little bit of homework on your part.
As was mentioned, this is the time to shine and standout especially if your sitting a the tail end or the middle of that pack (stats wise). Review your application. Is there anything you want to discuss further? Were those 175 character limits you struggled to stay under really all you had to say for those entries?
Show a little personality. I'm not talking about telling knock-knock jokes or anything. But they only know you from a list of things on your app and your statement. Maybe your statement is great, but most of the ones I have read are really serious and dry (which isn't necessarily a bad thing). Unless they invite you to interview, that's all they will know of you.
If you really think you've laid out your whole adult life on your application already and you feel like this is regurgitation no matter how hard you try, then submit and move on.
