Uncaught Error: Call to a member function get() on null

Hey,
my website throws an error when visiting it from google. The direct link is working. If I press F5 on the error screen, the page also loads.
In my logs, theres the following error:

AH01071: Got error 'PHP message: PHP Fatal error:  Uncaught Error: Call to a member function get() on null in /home/web-2/htdocs/wp-includes/query.php:28\nStack trace:\n#0 /home/web-2/htdocs/wp-includes/general-template.php(1288): get_query_var()\n#1 /home/web-2/htdocs/wp-content/plugins/wp-statistics/includes/class-wp-statistics-referred.php(70): wp_title()\n#2 /home/web-2/htdocs/wp-content/plugins/wp-statistics/includes/class-wp-statistics.php(331): WP_STATISTICS\\Referred::get()\n#3 /home/web-2/htdocs/wp-content/plugins/wp-statistics/includes/class-wp-statistics.php(115): WP_Statistics->instantiate()\n#4 /home/web-2/htdocs/wp-includes/class-wp-hook.php(287): WP_Statistics->plugin_setup()\n#5 /home/web-2/htdocs/wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters()\n#6 /home/web-2/htdocs/wp-includes/plugin.php(478): WP_Hook->do_action()\n#7 /home/web-2/htdocs/wp-settings.php(409): do_action()\n#8 /home/web-2/htdocs/wp-config.php(128): require_once('/home/web-2/htd...')\n#9 /home/web-2/htdocs/wp-load.php(37): require_once...', referer: https://www.google.com/

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