I've never had to emergency dismount... But while your learning maybe you could wear ankle supports just incase you don't land on the balls of your feet?
Haha speaking of emergency dismounts, my best friend did one at the local show off her 14.1hh pony (she's 16
) But it wasn't because something went wrong, more because she was doing a flag race with good old snuffy and she missed the pole you put the flag on, then all of a sudden she was in mid-air jumping off snuffy to put the flag on. Her mum and I are standing (well I was sitting on bubbles) on the sidelines cracking up, it was the funniest thing I've seen for a while, she never kicked out her stirrups it was just like she suddenly went up then came down beside snuffy running back to the pole (she landed on her feet too