Category Split Causes Critical Error

I’ve tried enabling category splitting but everytime I try I get the following critical error.

When seeking help with this issue, you may be asked for some of the following information:
WordPress version 5.9.1
Current theme:  (version )
Current plugin: Order Splitter for WooCommerce (version 4.5.0)
PHP version 8.0.16

Error Details
=============
An error of type E_ERROR was caused in line 5442 of the file /home/rossi/public_html/wp-content/plugins/woo-order-splitter/inc/functions.php. Error message: Uncaught TypeError: array_key_exists(): Argument #2 ($array) must be of type array, null given in /home/rossi/public_html/wp-content/plugins/woo-order-splitter/inc/functions.php:5442
Stack trace:
#0 /home/rossi/public_html/wp-includes/class-wp-hook.php(307): wc_os_settings_update('')
#1 /home/rossi/public_html/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters(NULL, Array)
#2 /home/rossi/public_html/wp-includes/plugin.php(474): WP_Hook->do_action(Array)
#3 /home/rossi/public_html/wp-admin/admin.php(175): do_action('admin_init')
#4 {main}
  thrown