CRITICAL Uncaught Error: Call to a member function get_cart_subtotal()

Hi,
I’ve got such an error:

CRITICAL Uncaught Error: Call to a member function get_cart_subtotal() on null in /mysite/public_html/wp-content/themes/customify/inc/compatibility/woocommerce/config/header/cart.php:385
Stack trace:
#0 /mysite/public_html/wp-content/themes/customify/inc/panel-builder/class-layout-builder-frontend.php(169): Customify_Builder_Item_WC_Cart->render(Array, Array)
#1 /mysite/public_html/wp-content/themes/customify/inc/panel-builder/class-layout-builder-frontend.php(455): Customify_Layout_Builder_Frontend->render_items()
#2 /mysite/public_html/wp-content/themes/customify/inc/panel-builder/builder-functions.php(77): Customify_Layout_Builder_Frontend->render()
#3 /mysite/public_html/wp-includes/class-wp-hook.php(286): customify_customize_render_header('')
#4 /mysite/public_html/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters('', Array)
#5 /home/u/una в /mysite/public_html/wp-content/themes/customify/inc/compatibility/woocommerce/config/header/cart.php on line 385

I work in a child theme. Woocommerce 3.6.4, WordPress 5.2.2, PHP 7.1.21
Any advice to fix the bug would be helpful