How do you know that the owner of the building that Sparky's was in, would not qualify for this deduction?
That's not the point. Even if they did qualify, you can't claim loss of income as an expense. In other words, you can't say "well, the market rate for this space is $30,000 per year but it was vacant, so I get a $30,000 deduction!". That's not how taxes work, at all. So this isn't an incentive to leaving a space vacant.