Updating a Calendar Event stored in CalDav from an email in RoundCube fails

Symptoms

When a calendar event is modified, a notification is sent to to the attendees with an ICS file to update their calendar's with the updated event information. However, if this event is currently stored in the CalDav Calendar, then attempting to import this updated ICS file in RoundCube will fail and show the following error:

PHP Error: No driver found for calendar "".

Description

We've opened an internal case for our development team to investigate this further. For reference, the case number is CPANEL-48420. Follow this article to receive an email notification when a solution is published in the product. 

Workaround

Delete the event in question from the CalDav Calendar, and "Accept" the updated invitation to have it be recreated with new information.