Fix ArcanistClosureLinter

Summary: Fixes T9498

Test Plan: Run arc lint with errors that get caught and reported by ArcanistClosureLinter

Reviewers: joshuaspence, epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: Korvin

Maniphest Tasks: T9498

Differential Revision: https://secure.phabricator.com/D14220