ERROR string + int

The Plugin never worked on this site for round about 2 months!
Got an email with this error:

WordPress-Version 5.7
Aktuelles Theme: Harrison (Version 1.3.1)
Aktuelles Plugin: WP Statistics (Version 13.0.7)
PHP-Version 8.0.1

Fehler-Details
==============
Ein Fehler vom Typ E_ERROR wurde in der Zeile 198 der Datei /data/web/.../wp-content/plugins/wp-statistics/includes/admin/templates/settings/externals.php verursacht. Fehlermeldung: Uncaught TypeError: Unsupported operand types: string + int in /data/web/.../wp-content/plugins/wp-statistics/includes/admin/templates/settings/externals.php:198
Stack trace:
#0 /data/web/.../wp-content/plugins/wp-statistics/includes/admin/templates/settings.php(50): include()
#1 /data/web/.../wp-content/plugins/wp-statistics/includes/admin/class-wp-statistics-admin-template.php(72): include('/data/web/1/000...')
#2 /data/web/.../wp-content/plugins/wp-statistics/includes/admin/pages/class-wp-statistics-admin-page-settings.php(61): WP_STATISTICS\Admin_Template::get_template(Array, Array)
#3 /data/web/.../wp-includes/class-wp-hook.php(292): WP_STATISTICS\settings_page::view('')
#4 /data/web/.../wp-includes/class-wp-hook.php(316): WP_Hook->apply_filters('', Array)
#5 /data/web/.../wp-includes/plugin.php(484): WP_Hook->do_action(Array)
#6 /data/web/.../wp-admin/admin.php(259): do_action('statistik_page_...')
#7 {main}
  thrown

HOPE this will help to fix the problem soon! The plugin was really god in the older versions!