It’s a business expense that you can deduct, no different than if you were renting it.

Net income = rent - expenses

If it’s not rented out you can still deduct the expense, and if negative you might be able to carry the loss forward.

But it's crappy because you have no rent to make up for the expense, so you're still losing money, just less than the full rent.

It's not like it's some magic trick or some perk landlord's get that magically gives them free money.

You can deduct your actual expenses, but you can’t deduct rent that you didn’t receive because the property was vacant, or get a “tax credit for unrented property” as was claimed.