My name is Lilith, I'm on the Social Care team at Shopify.
The error you're seeing is coming from your theme section for the newsletter subscription sign upfield.
If you recently made some edits to the theme code you'll want to roll the code back to an earlier version before those changes were made to your theme.
You can find this code under Online Store > Themes > Actions > Edit Code > Sections. There you'll find the section called
One thing that you'll want to remember is that if you have a page customizing or newsletter subscription app installed, you should check on those to make sure if they're changing that section as well.
If you're trying to edit something in your theme and are having some trouble coding the right snippets, I highly recommend hiring one of our partners to help you with this. You can find a suitable Shopify Partner in the Experts Marketplace or request a quote by following this guide here.
Let me know how you do with the information above! I'm happy to answer any questions you think of as you work on your business.