Fixes KeyError when resetting an input file
Fixes KeyError when resetting an input file

If the file hadn't been changed before trying to reset it, KeyError was
raised.

JosuaKrause/reprozip,JosuaKrause/reprozip,ViDA-NYU/reprozip,ViDA-NYU/reprozip,ViDA-NYU/reprozip,ViDA-NYU/reprozip,ViDA-NYU/reprozip,JosuaKrause/reprozip,JosuaKrause/reprozip