It's normal, your subevent won't ever trigger, as it will check if the spacebar has just been stroke only 1 time, this time being just after (like 0.01 ms after) the ball has been destroyed.
What you may want is to take your subevent out of its uper-event, so it can trigger on its own. You may also want to add a condition "spr_ball.count = 0" if what you want is to spanw a new ball after the previous one has been destroyed, once the player hits the space bar.