Error From Woocommerce

Recently after plugin upgrade we started to receive emails from WP about errors related to the swatches Pro plugin. Here is an error from the logs:

[08-Feb-2021 09:36:23 UTC] PHP Fatal error: Uncaught Error: Call to a member function get() on null in /var/www/html/wp-content/plugins/woo-variation-swatches-pro/includes/functions.php:9
Stack trace:
#0 /var/www/html/wp-includes/class-wp-hook.php(287): wvs_pro_cache_variation_ajax(Array)
#1 /var/www/html/wp-includes/plugin.php(212): WP_Hook->apply_filters(Array, Array)
#2 /var/www/html/wp-includes/functions.php(1465): apply_filters(‘nocache_headers’, Array)
#3 /var/www/html/wp-includes/functions.php(1487): wp_get_nocache_headers()
#4 /var/www/html/wp-includes/functions.php(3474): nocache_headers()
#5 /var/www/html/wp-includes/functions.php(3420): _default_wp_die_handler(‘<div class=”wp-…’, ‘WordPress &rsaq…’, Array)
#6 /var/www/html/wp-includes/class-wp-fatal-error-handler.php(233): wp_die(Object(WP_Error), ”, Array)
#7 /var/www/html/wp-includes/class-wp-fatal-error-handler.php(152): WP_Fatal_Error_Handler->display_default_error_template(Array, Object(WP_Error))
#8 /var/www/html/wp-includes/class-wp-fatal-error-handler.php(57): WP_Fatal_Error_Han in /var/www/html/wp-content/plugins/woo-variation-swatches-pro/includes/functions.php on line 9

Do you have idea what can be the reason of this error?