Cannot deactivate plugin

Hello, I get an error from login-designer and it does not go away even after deactivating the plugin:

Fatal error: Uncaught Error: Call to a member function get_page_permastruct() on null in /var/home/my-domain_at/www/neu/wp-includes/link-template.php:431 Stack trace: #0 /var/home/my-domain_at/www/neu/wp-includes/link-template.php(393): _get_page_link(Object(WP_Post), false, false) #1 /var/home/my-domain_at/www/neu/wp-includes/link-template.php(197): get_page_link(Object(WP_Post), false, false) #2 /var/home/my-domain_at/www/neu/wp-content/plugins/login-designer/login-designer.php(236): get_permalink(Object(WP_Post)) #3 /var/home/my-domain_at/www/neu/wp-content/plugins/login-designer/login-designer.php(68): Login_Designer->login_designer() #4 /var/home/my-domain_at/www/neu/wp-content/plugins/login-designer/login-designer.php(668): Login_Designer::instance() #5 /var/home/my-domain_at/www/neu/wp-content/plugins/login-designer/login-designer.php(672): login_designer() #6 /var/home/my-domain_at/www/neu/wp-settings.ph in /var/home/my-domain_at/www/neu/wp-includes/link-template.php on line 431