Fatal error (apparently while trying to set a transient)

Fatal error: Uncaught Error: Call to a member function get() on null in /var/www/wordpress/wp-includes/query.php:28 Stack trace: #0 /var/www/wordpress/wp-content/plugins/strong-testimonials/includes/class-strong-testimonials-order.php(55): get_query_var(‘paged’) #1 /var/www/wordpress/wp-includes/plugin.php(600): Strong_Testimonials_Order->store_query_vars(Object(WP_Query)) #2 /var/www/wordpress/wp-includes/query.php(2503): do_action_ref_array(‘pre_get_posts’, Array) #3 /var/www/wordpress/wp-includes/query.php(4050): WP_Query->get_posts() #4 /var/www/wordpress/wp-includes/query.php(4161): WP_Query->query(Array) #5 /var/www/wordpress/wp-content/themes/wp-simple/parts/frontpage-featured.php(32): WP_Query->__construct(Array) #6 /var/www/wordpress/wp-includes/template.php(574): require(‘/var/www/wordpr…’) #7 /var/www/wordpress/wp-includes/template.php(531): load_template(‘/var/www/wordpr…’, false) #8 /var/www/wordpress/wp-includes/general-template.php(167): locate_template(Array, true, false) #9 /var/www/wordpress/wp-conte in /var/www/wordpress/wp-includes/query.php on line 28

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