Reset vals after user types in address field

This should fix this bug on both from and to. It should also fix the issue where the incorrect address was showing on the overview page.

fixes CG-CamSys/Backlog#250 "The Locations Displayed On The Overview Screen And Those In The Trip Results Are Not Always Necessarily The Same"

fixes CG-CamSys/Backlog#248 "If legitimate address has been entered once, after hitting the Back button or Make Changes, it is possible to enter non-addresses and not receive the error message"