By rule both spots must be filled. But with only one player how can I enforce that rule? Actually, there should be no shot until both are filled... therefore, I think you've already made your decision of NO VIOLATION. So play on. Good Luck A1 - get the rebound and stall.
I wouldn't want to be the official on the floor with my arm out for the free-throw violation and letting some slacker shoot until he makes two. Then give the ball to A1 to attempt a throw-in as all of Team B backs away to the division line and plays dodge-ball.... and no time clicks off the clock. Ooohh let's do this some more.
It's a good thing you are the Ref, JR, so you can make these tough, beyond the rule book, decisions.
