Fix fatal saving menu items without custom validation

Summary: Fixes T12142. Correct spelling of method.

Test Plan: Edit the name of a Details menu item in projects, or add a divider.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T12142

Differential Revision: https://secure.phabricator.com/D17240