Let it fall.
Incidentally, I personally extend this rule to rounds jacked out of an ejection port: I'm all the time seeing people clear their pistol and do one of two things:
- Either they try and catch the ejected round in midair, which looks neat and all, but while they're trying to play Joe Cool, with their attention focused on that glittering piece of flying brass, an appalling number of them forget that... Hey! Ken Griffey Jr.! You've still got a pistol in your other hand while you're trying to run down that pop fly!
- Or they carefully place their hand over the ejection port so that the precious live round, costlier and more delicate than a Fabergé egg, can be gently cradled. Which is great, but again, too much attention is being focused on the ejected round and not enough on, you know, the gun. Besides, with you trapping it in the ejection port, if your hand on the slide slips, you're going to get a palmful of red-hot brass shards when the primer gets slammed up against something by the closing slide.