Fix the last remaining (?) continue inside switch

Summary: See https://discourse.phabricator-community.org/t/error-on-project-creation-or-edition-with-php7-3/2236/. This is the only remaining case that the linter rule in D19931 detected in libphutil, arcanist, or Phabricator.

Test Plan: Ran arc lint --everything ... in all three repositories, only hit this one.

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D19932