Small change needed for Top menus.

[StonehengeCreations]

When creating a Top level menu you get an error: Notice: Undefined index: in/wp-content/plugins/Admin-Page-Class-master/admin-page-class/admin-page-class.php on line 277

In the current version of Wordpress the "top" was dropped, I guess. Deleting the substring corrects the error. Original line 277: $this->Top_Slug = $args['menu']['top'];

Edited and working line 277: $this->Top_Slug = $args['menu'];

Sorry! Completely new to contributing to Github, so I haven't figured out how to add the edited file yet.. ;-)