What does this PR do?

• Fixes #9485 (GitHub issue number)

/claim #9485

Visual Demo (For contributors especially)

A visual demonstration is strongly recommended, for both the original and new change (video / image - any one).

Video Demo (if applicable):

• Show screen recordings of the issue or feature.
• Demonstrate how to reproduce the issue, the behavior before and after the change.

Image Demo (if applicable):

• Add side-by-side screenshots of the original and updated change.
• Highlight any significant change(s).

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. NA
• I confirm automated tests are in place that prove my fix is effective or that my feature works. Could you point me out where to write the test case

How should this be tested?

• Launch local Caldav server radicale
• Connect to radicale and schedule event
• Check the event.ics received in radicale server

ORGANIZER;CN=Yvon:mailto:test@example.com;SCHEDULE-AGENT=CLIENT
ATTENDEE;RSVP=TRUE;ROLE=REQ-PARTICIPANT;PARTSTAT=ACCEPTED;CN=Yufan Wu:mailt
	o:abc@example.com;SCHEDULE-AGENT=CLIENT

Checklist

• I haven’t read the contributing guide
• My code doesn’t follow the style guidelines of this project
• I haven’t commented my code, particularly in hard-to-understand areas
• I haven’t checked if my changes generate no new warnings