Channel: clicking auf "Subscribe" when not logged in still updates the subscriber count

Steps to reproduce

• create a channel
• log out
• go on the page of the channel https://demo.funkwhale.audio/api/v1/channels/mychannel/rss
• click on subscribe

What happens?

The count of subscribers will be updated, although there is nothing to subscribe as you are not logged in. It can even go in the negatives, because the Subscribe button has the same "state" as the last user logged in: if the user followed the channel, then you can only unsubscribe it, so it goes in the negatives...

What is expected?

Subscribe should only work for logged in users. Either the button should be completely removed when not logged in (easy fix), or clicking on it should pop up the login page

Context

Funkwhale version(s) affected: 1.0.1