Fatal error please help

Hi I got this fatal error in woocommerce, am using the latest update now but advice, please. www.logjam.net thanks. It's obviously a huge problem as we may be losing orders, here! 2019-06-06T10:11:05+00:00 CRITICAL Uncaught Error: Call to a member function get_cart_subtotal() on null in /www2/32e/www.logjam.net/web/wp-content/themes/audioman-pro/inc/customizer/woocommerce.php:193 Stack trace: #0 /www2/32e/www.logjam.net/web/wp-content/themes/audioman-pro/inc/customizer/woocommerce.php(172): audioman_cart_link() #1 /www2/32e/www.logjam.net/web/wp-content/themes/audioman-pro/template-parts/navigation/navigation-primary.php(18): audioman_header_cart() #2 /www2/32e/www.logjam.net/web/wp-includes/template.php(724): require('/www2/32e/www.l...') #3 /www2/32e/www.logjam.net/web/wp-includes/template.php(671): load_template('/www2/32e/www.l...', false) #4 /www2/32e/www.logjam.net/web/wp-includes/general-template.php(168): locate_template(Array, true, false) #5 /www2/32e/www.logjam.net/web/wp-content/themes/audioman-pro/header.php(31): get_template_part('template-parts/...', 'primary') #6 /www2/32e/www.logjam.net/web/wp-includes/template.php(722): require_once('/www2/32e/www.l...') #7 /www2/32e/www.logjam.net/web/wp-includes/temp in /www2/32e/www.logjam.net/web/wp-content/themes/audioman-pro/inc/customizer/woocommerce.php on line 193