Show ical and Google Calendar links for non-public events
Currently, the Download iCalendar entry for this event and Add event to Google Calendar links only appear in event confirmation emails, on the event confirmation page and on the event info page if the event is public.
But if someone has registered for an event, they should be able to add that event to their calendar regardless of whether it is public or not. The event info page can also include these links as the calendar links contain the same information as is already found on the page.
For reference, the help text for Public Event says: "When enabled, this event will be included in iCalendar feeds and displayed on your site's "Upcoming Events" block." So there shouldn't be any expectation that we're hiding calendar links for non-public events as this settings controls only calendar feeds. Can't see any reason we'd want to hide calendar links, in any case.
Turns out the links fail when the event is non-public, so I'll have to fix that first.