[ticket/12862] Fix pop-up box wraps

Quick fix for body background in popups showing through wrap as their is no bg-color or styling applied to the simple-wrap.

This is a quick fix as these should all really be handled via ajax modals similar to the message box

Ticket: https://tracker.phpbb.com/browse/PHPBB3-12862?jql=project%20%3D%20PHPBB3

PHPBB3-12862