errors when updated wordpress and woocommerce

I’m getting these errors.

Notice: Undefined index: menu_position in /home/mysite/public_html/exp.mysite.com/wp-content/plugins/personalize-woocommerce-cart-page/classes/admin.class.php on line 129

Warning: Cannot modify header information – headers already sent by (output started at /home/mysite/public_html/exp.mysite.com/wp-content/plugins/personalize-woocommerce-cart-page/classes/admin.class.php:129) in /home/mysite/public_html/exp.mysite.com/wp-includes/pluggable.php on line 1196

I’m using a subdomain to test everything before I go live and want to fix this so I can go live with all the updates.

I can find the references in the files referred, but I don’t know what to do about it.

Thanks.

https://wordpress.org/plugins/personalize-woocommerce-cart-page/