R1:2189b6df6d88

Fix slowvote exception when viewing description diff

Summary: Fixes T6937. We weren't passing required parameters.

Test Plan: Followed repro steps in task.

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Maniphest Tasks: T6937

Differential Revision: https://secure.phabricator.com/D11346