Same here. Tested on multiple websites. Here’s the error:
Fatal error: Uncaught Error: Call to a member function switch_to_locale() on null in /home/customer/www/***.com/public_html/wp-includes/l10n.php:1679 Stack trace: #0 /home/customer/www/***.com/public_html/wp-admin/includes/misc.php(132): switch_to_locale('en_US') #1 /home/customer/www/***.com/public_html/wp-content/plugins/http-headers/http-headers.php(1330): insert_with_markers('/home/customer/...', 'HttpHeaders', Array) #2 /home/customer/www/***.com/public_html/wp-content/plugins/http-headers/http-headers.php(815): update_headers_directives() #3 /home/customer/www/***.com/public_html/wp-includes/class-wp-hook.php(309): http_headers_option('siteground_opti...') #4 /home/customer/www/***.com/public_html/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters('', Array) #5 /home/customer/www/***.com/public_html/wp-includes/plugin.php(474): WP_Hook->do_action(Array) #6 /home/customer/www/***.com/public_html/wp-includes/option.php(538): do_action('updated_opt in /home/customer/www/***.com/public_html/wp-includes/l10n.php on line 1679