Select markers dropdown doesn't behave as expected

[philipstarkey]

I loaded a shot, deleted the shot, loaded the same shot again, and ended up with 2 entries for the same shot in the "select markers" drop down. Removing the shot for the second time caused one of them to grey out, but not the other. Something is off about how the dropdown list is populated and cleaned. To be honest, I'm not even sure why items are not just removed from that list when the shot is removed.