"Undefined" message when adding item to cart

Hello,

I have a custom add_to_cart.php loop based on this template: https://gist.github.com/claudiosmweb/5114131

On the archive page, when “Add to Cart” is clicked, it shows it as “Undefined” for a second before going back to “Add to Cart”. Screenshot: https://imgur.com/LveFbxi

If I delete the custom loop files it works fine and no one else seems to be having the issue. Is there something I’m missing?

Thanks for your help!

https://www.ads-software.com/plugins/woocommerce/