Not Found, Error 404

Fatal error: Uncaught Error: [] operator not supported for strings in /home/conflict_admin/public_html/wp-content/plugins/bbpress/includes/forums/functions.php:1854 Stack trace: #0 /home/conflict_admin/public_html/wp-includes/class-wp-hook.php(298): bbp_pre_get_posts_normalize_forum_visibility(Object(WP_Query)) #1 /home/conflict_admin/public_html/wp-includes/class-wp-hook.php(323): WP_Hook->apply_filters('', Array) #2 /home/conflict_admin/public_html/wp-includes/plugin.php(515): WP_Hook->do_action(Array) #3 /home/conflict_admin/public_html/wp-includes/class-wp-query.php(1688): do_action_ref_array('pre_get_posts', Array) #4 /home/conflict_admin/public_html/wp-includes/class-wp-query.php(3267): WP_Query->get_posts() #5 /home/conflict_admin/public_html/wp-includes/class-wp-query.php(3376): WP_Query->query(Array) #6 /home/conflict_admin/public_html/wp-content/plugins/bbpress/includes/common/widgets.php(784): WP_Query->__construct(Array) #7 /home/conflict_admin/public_html/wp-includes/class-wp-widget.php(395): BBP_Topics_Widge in /home/conflict_admin/public_html/wp-content/plugins/bbpress/includes/forums/functions.php on line 1854