Uncaught Error: in_array(): Argument #2 ($haystack) must be of type array

Hi, on my customers site the whole website is not accessible anymore once Auto coupons plug-in is activated. It worked fine all the time, but since yesterday it’s throwing the following error. Happened with 3.0.28 and keeps happening after updating to 3.0.29. The website works fine again once we deactivate the plug-in.

Uncaught Error: in_array(): Argument #2 ($haystack) must be of type array, string given
in /usr/www/users/frauei/wp/wp-content/plugins/woo-auto-coupons/wac_functions.php on line 527

Call stack:

1. in_array()
   wp-content/plugins/woo-auto-coupons/wac_functions.php:527
2. wac_qty_in_cart()
   wp-content/plugins/woo-auto-coupons/wac_functions.php:650
3. wac_apply_coupons()
   wp-includes/class-wp-hook.php:324
4. WP_Hook::apply_filters()
   wp-includes/class-wp-hook.php:348
5. WP_Hook::do_action()
   wp-includes/plugin.php:517
6. do_action()
   wp-content/plugins/woocommerce/includes/class-wc-cart-session.php:222
7. WC_Cart_Session::get_cart_from_session()
   wp-includes/class-wp-hook.php:324
8. WP_Hook::apply_filters()
   wp-includes/class-wp-hook.php:348
9. WP_Hook::do_action()
   wp-includes/plugin.php:517
10. do_action()
    wp-settings.php:726
11. require_once('/usr/www/users/xxx/wp/wp-settings.php')
    wp-config.php:116
12. require_once('/usr/www/users/xxx/wp/wp-config.php')
    wp-load.php:50
13. require_once('/usr/www/users/xxx/wp/wp-load.php')
    wp-blog-header.php:13
14. require('/usr/www/users/xxx/wp/wp-blog-header.php')
    index.php:17

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