I am using a custom field to dynamically associate sub-navigation menus with specific pages. This code works well, but it does not gracefully fallback to NO menu when no MenuName custom field exists, instead displaying the default menu.
I have tried both 'fallback_cb' => 'false' and 'fallback_cb' => '' with no success. Any ideas?
I should also mention I’m using this in a child theme of Twenty Eleven. I saw that fallback_cb can be affected by a pre_get_posts filter, or potentially another entry in functions.php – I have looked through and do not see any pre_get_posts filters.