Variable initialized with value of inappropriate type

[ipm-frommen]

Everywhere in the _wp_menu_output function, the $submenu_items variable is treated like an array; so why not initialize it with array(), instead of false?

There are several ! empty( $submenu_items ) checks, and these work perfectly fine with $submenu_items being an empty array.

[SergeyBiryukov]

In 31364:

In _wp_menu_output(), $submenu_items is an array and should be initialized as such.

props ipm-frommen.
fixes #31257.