Feeds of non-existent tags and categories displays an empty feed instead of 404

[rafaucau]

I noticed in Google Search Console that Google often visits feeds of tags that no longer exist. It turns out that the RSS feeds still work instead of returning a 404.

Recreating the issue is simple:
Go to the page of the non-existent tag, e.g. /tag/asdsdsad/ and append feed/ to the end of the address, eg. /tag/asdsdsad/feed/. An empty feed will be displayed instead of a 404.

This should return a 404 so that search engine bots can forget about it instead of fetching it every so often.
I have thousands of such deleted tags on my site. It would be better for the environment if the bots didn't waste resources on this.

[rafaucau]

Non-existent tag

[rafaucau]

Feed of this tag.