Template tags visible on frontend when field doesn't exist

We're using GeneratePress Elements to add page headers across a website. Most of these pages uses a {{custom_field.subtitle}} to output the subtitle custom field. This works great except for pages where that subtitle doesn't, or can't, exist. An example of one of these pages is here: https://www.rockinroadtrip.com/2021/08/

As you can see, the {{custom_field.subtitle}} is visible on the frontend because we have no custom fields on those date archives. I would rather this didn't show {{custom_field.subtitle}} when empty/missing.

We're already using ACF to add a "subtitle" custom field to prevent this issue from happening on category archives but that's not possible, or reasonable, on date archives.

Any ideas? Recommendations? Updates to Elements?