This happens to me very, very rarely and I usually just start slowly to let it complete the shift the shift back once I'm moving or I click back to undo. I don't like to shift chainrings unless I really need to, shifting chainrings takes too long IMHO. Also, I usually ride with panniers so lifting the rear wheel isn't a viable option either for me, but that may work well for light bikes. There are few options to deal with this so one needs to chose what shifts... umm suits them best