Fix an issue with AuthProviderConfig handles

Summary: Fixes T11156. These were never correct, but also never actually used until I made timelines load object handles unconditionally in D16111.

Test Plan: Viewed an auth provider with transactions, no more fatal.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11156

Differential Revision: https://secure.phabricator.com/D16128