Administration: Don't unnecessarily escape none or div in the adm…

…in menu.

This matches a similar conditional in `wp-admin/menu-header.php`, where these values are handled as special cases and don't output the default menu image so that an icon could be added to `div.wp-menu-image` as CSS background. 

Follow-up to [9578], [21877], [26664].

Props andrewleap, ironprogrammer, azaozz.
Fixes #58361.

git-svn-id: https://develop.svn.wordpress.org/trunk@57159 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/menu.php

@@ -127,8 +127,11 @@
 
 	$menu_icon = 'dashicons-admin-post';
 	if ( is_string( $ptype_obj->menu_icon ) ) {
-		// Special handling for data:image/svg+xml and Dashicons.
-		if ( str_starts_with( $ptype_obj->menu_icon, 'data:image/svg+xml;base64,' ) || str_starts_with( $ptype_obj->menu_icon, 'dashicons-' ) ) {
+		// Special handling for an empty div.wp-menu-image, data:image/svg+xml, and Dashicons.
+		if ( 'none' === $ptype_obj->menu_icon || 'div' === $ptype_obj->menu_icon
+			|| str_starts_with( $ptype_obj->menu_icon, 'data:image/svg+xml;base64,' )
+			|| str_starts_with( $ptype_obj->menu_icon, 'dashicons-' )
+		) {
 			$menu_icon = $ptype_obj->menu_icon;
 		} else {
 			$menu_icon = esc_url( $ptype_obj->menu_icon );