Prevents crash when both url and enclosure_url dont exist

[naps62]

this commit made the whole process fail when both url and enclosure_url do not exist. The reason is that entry.enclosure_url.present? throws an error, since the method doesn't exist at all

There's actually a much larger issue here, which is the error being silently hidden in FetchFeed, which just rescues every exception and flags the feed as red. This makes it very hard to debug errors

However I just fixed this one issue. I hope after re-deploying, my feeds will start working again, otherwise I'll have to get back at it

[naps62]

FYI: just tested this on my running instance in Heroku. Previously, most feeds were not updating, due to a parsing error. After this fix, they started working (only one is still failing, I'll have to investigate that one later)

[gabrielpoca]

I also tested locally 👍