MDL-73402 block_admin_bookmarks: slightly relax section cleaning.

Allow '/' character in external page names.

blocks/admin_bookmarks/create.php

@@ -30,7 +30,8 @@ $context = context_system::instance();
 $PAGE->set_context($context);
 $adminroot = admin_get_root(false, false);  // settings not required - only pages
 
-if ($section = optional_param('section', '', PARAM_SAFEDIR) and confirm_sesskey()) {
+// We clean section with safe path here for compatibility with external pages that include a slash in their name.
+if ($section = optional_param('section', '', PARAM_SAFEPATH) and confirm_sesskey()) {
 
     if (get_user_preferences('admin_bookmarks')) {
         $bookmarks = explode(',', get_user_preferences('admin_bookmarks'));