Custom-coded menu not displayed when custommenuitems is empty

RECREATE

In a custom theme renderers.php, override render_custom_menu() and add some hard-coded menu item. e.g:

<?php

class theme_zebra_core_renderer extends core_renderer {

  protected function render_custom_menu(custom_menu $menu) {

    $menu->add('Home', new moodle_url('/'));

    return parent::render_custom_menu($menu);

  }

}

Browse to /admin/settings.php?section=themesettings and configure custommenuitems to be blank (no spaces, no new lines). Save.

EXPECTED RESULTS

The Home menu item will be displayed.

ACTUAL RESULTS

No custom menu items are displayed

CODE

The culprit for this unexpected behavior occurs in lib/outputrenderers.php in function custom_menu:

        if (empty($custommenuitems)) {

            return '';

        }

By returning an empty string when the configured $custommenuitems is blank, the overridden render_custom_menu() is never executed