Events in iCal feed have incorrect links

One-sentence description

Notice the double https://https://

I believe the html only shows because my calendar (macOS calendar) doesn't support it

Current behaviour / Reproducing the bug

1. Have an event in the calendar
2. Look at the event in an external calendar application (via iCal feed)
3. The link to more information on the website does not work as it is malformed

Expected behaviour

Links in the iCal feed have the correct https:// prefix