Just had an empty row situation on a 752 the other day. Based on my record keeping, I have had three empty rows within the last 12 months, and all 752s, pure coincidence!
How do you predict an empty row? You don't. The odds of getting an empty row is extremely unlikely these days, it's usually wishful thinking hoping for an empty row. The exception may due to no shows, misconnect, or some other irrop scenarios.