fix bug where conductor is trying to complete nonexisting contracts
fix bug where conductor is trying to complete nonexisting contracts

(fixes #454)

CityofPittsburgh/pittsburgh-purchasing-suite,codeforamerica/pittsburgh-purchasing-suite,codeforamerica/pittsburgh-purchasing-suite,CityofPittsburgh/pittsburgh-purchasing-suite,CityofPittsburgh/pittsburgh-purchasing-suite,codeforamerica/pittsburgh-purchasing-suite,CityofPittsburgh/pittsburgh-purchasing-suite,codeforamerica/pittsburgh-purchasing-suite