Problem when creating a Child-Theme

Hi,
When trying to create a child theme, using the “Child Theme Configurator” plugin I get this error:

The theme generated unexpected PHP debug output.

Notice:  Undefined index: redirect_to in C:\xampp\htdocs\xxx\wp-content\plugins\shopify-ecommerce-shopping-cart\includes\class-output.php on line 97

Please contact this Theme's author and report the items above. You may or may not be able to use this Theme as a Child Theme while these conditions exist.
It is possible that this theme has specific requirements to work correctly as a child theme. Please make sure you are using the latest version of this theme and check your theme's documentation for more information.

Hope you can help me find out what this is about. I found this site online that seems to be having the same issue? http://www.freshtips.com/shocking-gross-things-dentists-find-in-mouths

https://wordpress.org/plugins/shopify-ecommerce-shopping-cart/