Prevent exceptions when adding repositories via conduit.

Summary: Simple change to stop exceptions from being thrown based on the diff in D4146.

Test Plan: arc call-conduit repository.create

Reviewers: epriestley, btrahan

Reviewed By: btrahan

CC: vrana, aran, Korvin

Maniphest Tasks: T2268

Differential Revision: https://secure.phabricator.com/D4342