Plugin Error, creates critical error

Hello:

We upgraded to the newest WordPress and people couldn’t add anything to the cart it would generate an error:

There has been a critical error on your website.

Learn more about debugging in WordPress.

My server support said the problem was your plugin, so I had to disable it. (see below). Any help is appreciated.

Paul

It looks like there is some issue with your Woocommerce-advanced-shipping plugin and that is what is causing the shopping cart to fail.

Here is the error we are seeing on here:

Fatal error: Uncaught Error: [] operator not supported for strings in /home/barne/public_html/wp-content/plugins/woocommerce-advanced-shipping/includes/class-was-method.php:91
Stack trace:

0 /home/barne/public_html/wp-content/plugins/woocommerce-advanced-shipping/includes/class-was-method.php(31): WAS_Advanced_Shipping_Method->was_match_methods()
1 /home/barne/public_html/wp-content/plugins/woocommerce-advanced-shipping/woocommerce-advanced-shipping.php(181): WAS_Advanced_Shipping_Method->__construct()
2 /home/barne/public_html/wp-includes/class-wp-hook.php(288): WooCommerce_Advanced_Shipping->was_shipping_method(”)
3 /home/barne/public_html/wp-includes/class-wp-hook.php(312): WP_Hook->apply_filters(NULL, Array) #4 /home/barne/public_html/wp-includes/plugin.php(478): WP_Hook->do_action(Array)
5 /home/barne/public_html/wp-content/plugins/woocommerce/includes/class-wc-shipping.php(120): do_action(‘woocommerce_shi…’)
6 /home/barne/public_html/wp-content/plugins/woocommerce/includes/class-wc-shipping.php(112): WC_Shi in /home/barne/public_html/wp-content/plugins/woocommerce-advanced-shipping/includes/class-was-method.php on line 91

The page I need help with: [log in to see the link]