Sitemap error

Hi there,
I added my sitemaps to the Google search console and 1 out of the 4 URLs is empty and returns a “This required tag is missing. Please add it and resubmit.” error.

https://montenegrotower.com/post_tag-sitemap1.xml

Is that sitemap required or can it be removed? When I create the sitemaps in SEOPress, it adds that XML despite being empty.

Not sure if its required? If the empty one would not be included, maybe I can get rid of my error message.

Thanks
Chris