Taxonomies on attachments should not generate UI is show_ui is false

[simonwheatley]

Currently if you register a taxonomy and associate it with attachments, the show_ui argument does not affect whether WordPress generates the UI for the taxonomy in the media item edit form. If show_ui is false, then no UI should be generated anywhere in any admin screen.

$args = array(
	'label'   => 'Test Taxonomy',
	'show_ui' => false,
	);
register_taxonomy( 'test', array( 'attachment' ), $args );

Patch to prevent taxonomy fields showing on media item edit form if show_ui is false

Fix seems pretty simple, just check for show_ui in get_attachment_fields_to_edit at the same point as we check for the public argument. See patch above.

Before doing this, I just wanted to confirm that show_ui is true by default for register_taxonomy(). That is the case, so I am good with this.

show_ui is null by default, and falls through to the value of public, which is true by default.

In [21240]:

Hide UI for Attachment taxonomies if show_ui is false for that taxonomy. props simonwheatley. fixes #21104