Activity Add To Calendar not producing valid ics file

[brettski]

Describe the bug Add to calendar button not working on Activities

To Reproduce Steps to reproduce the behavior:

1. Go to an activity, e.g. http://localhost:5000/activities/EwBiyHRzf7oWBhiz8YPL
2. Click on Add To Calendar
3. If you look in the console, you'll see an error...
4. You are prompted with an ics file to download, though this file does not contain an .ics document

Expected behavior A valid .ics document downloaded when clicking "Add To Calendar"

Screenshots Error in Console:

Additional context Add any other context about the problem here.