WebCal events not displayed in Grid

## What Happened

I added a calendar subscription to my Nextcloud backend in order to display holidays in elementary Calendar. To achieve this, I copied the iCal URL from here https://www.feiertagskalender.ch/export.php?geo=1638&jahr=2021&klasse=5&hl=de and added it to my Nextcloud.

Then I resynced in Evolution and the calendar and its events appeared there correctly:


However, elementary Calendar does seem to render the events in the sidebar - but does not show them in the main event grid:


## Platform Information

I'm running the elementary OS 6 Pre-Release version.

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