Plugin confilct(s) - EE_Admin_Page passes null to 'add_meta_boxes' for both $post_type and $post

[Pebblo]

Within admin_details_wrapper.template.php we use:

do_action('add_meta_boxes', $post_type, $post);

This is causing issues with some plugins as they have a type declaration of string for $post_type and it breaks our admin pages as they are null within EE.

The latest example is with SearchWP:

Fatal error: Uncaught Error: Argument 1 passed to SearchWP\Sources\Attachment::document_content_meta_box() must be of the type string, null given, 
called in \wp-includes\class-wp-hook.php on line 289
in \wp-content\plugins\searchwp\includes\Sources\Attachment.php on line 390

To Reproduce
Install SearchWP and active, then go to Event Espresso -> General Settings, Calendar, Payment methods, maintenance etc.

Or, add a callback to add_meta_boxes that requires $post_type is passed as a string and visit the above.

Screenshots
https://monosnap.com/file/1bFEhwMAzi0FtNml75zwCJDIH7omhO
(The kint output at the top of the page is me confirming what whose globals are)

[Pebblo]

Fixed in #3361.

Closing out.