There has been a critical error on your website

We just installed the plugin, but it gives the error: There has been a critical error on your website

When we disable the plugin, We can place orders.

here are the error logs

2020-06-02T16:07:31+05:30 CRITICAL Uncaught Error: Call to a member function get_value() on string in /wp-content/plugins/woo-delivery/public/class-coderockz-woo-delivery-public.php:256
Stack trace:
#0 /wp-includes/class-wp-hook.php(287): Coderockz_Woo_Delivery_Public->coderockz_woo_delivery_add_custom_field(”)
#1 /wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters(”, Array)
#2 /wp-includes/plugin.php(478): WP_Hook->do_action(Array)
#3 /wp-content/plugins/woocommerce/templates/checkout/form-checkout.php(52): do_action(‘woocommerce_che…’)
#4 /wp-content/plugins/woocommerce/includes/wc-core-functions.php(251): include(‘/home/upxryevw/…’)
#5 /wp-content/plugins/woocommerce/includes/shortcodes/class-wc-shortcode-checkout.php(294): wc_get_template(‘checkout/form-c…’, Array)
#6 /home/upxryevw/ in /wp-content/plugins/woo-delivery/public/class-coderockz-woo-delivery-public.php on line 256