plugin upgrade

I am running a website under php 7.2.12-1
Once I upgrade the plugin, the website stops running and I receive a white page and in wp-admin

I use also Email Notifications for WP Security Audit Log which is up to date

The errors I see when entering wp-admin:
error code 200
and
Error thrown

Call to a member function AddPremiumPlugin() on null

[php7:warn] [pid 24274] [client 185.28.155.130:57228] PHP Warning: Declaration of Roots_Walker_Comment::start_el(&$output, $comment, $depth, $args, $id = 0) should be compatible with Walker_Comment::start_el(&$output, $comment, $depth = 0, $args = Array, $id = 0) in /var/www/html/strauss-group/wp-content/themes/retlehs-roots-43f44a4/lib/comments.php on line 0

please advice