The error has nothing to do with Tagify, seems that the where formatter is generating the error. It will be difficult for me to replicate, but from the error it looks like the get_user_site_listings.data.brand_user_listings.values('person_profile_id') part returns undefined. Please validate that that part is actually returing an array.
This can happen when that data is not yet loaded. I can add extra validation in the code to prevent the error and only show a warning in the console.