Customize: Fix ability to shift-click on placeholder/pre-saved nav menu items...

Customize: Fix ability to shift-click on placeholder/pre-saved nav menu items in preview to focus on corresponding control.

Fixes #39102.

Built from https://develop.svn.wordpress.org/trunk@39562


git-svn-id: https://core.svn.wordpress.org/trunk@39502 1a063a9b-81f0-0310-95a4-ce76da25c4cd