Stack trace:
#0 /home/bonusfunnel.com/public_html/wp-content/plugins/master-popups-lite/includes/class-functions.php(549): implode()
#1 /home/bonusfunnel.com/public_html/wp-content/plugins/master-popups-lite/includes/class-popups.php(272): MasterPopups\Includes\Functions::url_google_fonts()
#2 /home/bonusfunnel.com/public_html/wp-content/plugins/master-popups-lite/includes/class-popups.php(247): MasterPopups\Includes\Popups->get_link_google_fonts()
#3 /home/bonusfunnel.com/public_html/wp-includes/class-wp-hook.php(303): MasterPopups\Includes\Popups->add_popups_to_admin_footer()
#4 /home/bonusfunnel.com/public_html/wp-includes/class-wp-hook.php(327): WP_Hook->apply_filters()
#5 /home/bonusfunnel.com/public_html/wp-includes/plugin.php(470): WP_Hook->do_action()
#6 /home/bonusfunnel.com/public_html/wp-admin/admin-footer.php(78): do_action()
#7 /home/bonusfunnel.com/public_html/wp-admin/post.php(369): require_once('...')
#8 {main}
thrown
generate_do_element_classes() is a new function in GP 2.2.
If your child theme is using it, you need to make sure your parent theme is running at least 2.2.
In that case, the function should be defined: https://github.com/tomusborne/generatepress/blob/2.2.1/inc/markup.php#L20
Perhaps your server has caching which is still serving the old files?
Let me know if that helps or not?
