Allow to call parent_dropdown() for an arbitrary post

[charliespider]

parent_dropdown() can no longer be used outside of the loop, such as within the wp-admin, because an E_NOTICE will be emitted in template.php:683 since $post is null.

A simple fix is to change the function argument declarations from

function parent_dropdown( $default = 0, $parent = 0, $level = 0 ) {

to:

function parent_dropdown( $default = 0, $parent = 0, $level = 0, $post = array() ) {

and then also change:

$post = get_post();

to

	if ( empty( $post )) {
		$post = get_post();
	}	

which would allow a WP post object to be passed into the function.

Sorry I am unable to provide an SVN patch.

[SergeyBiryukov]

an E_NOTICE will be emitted in template.php:683 since $post is null.

#23026 would fix the notice introduced in [21735].

Renaming the ticket to better reflect its purpose.

[wonderboymusic]

In 34111:

Add an argument to parent_dropdown(), $post, to allow it to be called for an arbitrary post.

Fixes #23162.

[wonderboymusic]

In 34113:

Add sanity checks in map_meta_cap(), return 'do_not_allow' when posts don't exist.

Adds unit test.

Props ocean90, nerrad, filosofo.
Fixes #23162.