make_csv fails with ghost events.

[Guiraud]

For this kind of event a copy of a recurred event, a undocumented tag is created : X-MOZ-FAKED-MASTER:1
this behaviour has been identified :
https://bugzilla.mozilla.org/show_bug.cgi?id=536796
Some how it's not corrected in Thunderbird.

BEGIN:VEVENT
CREATED:20210118T075836Z
LAST-MODIFIED:20210118T075906Z
DTSTAMP:20210118T075906Z
UID:3BE58C04-1B6C-4C1E-8AA9-60A0F3A25864
ATTENDEE;EMAIL=nnnnn@mmmmm.tld;RSVP=TRUE;PARTSTAT=ACCEPTED;CN=Me
 hdi Guiraud;CUTYPE=INDIVIDUAL:mailto:nnnnn@mmmmm.tld
RDATE;VALUE=DATE-TIME:20210120T090000Z
DTSTART;TZID=Europe/Paris:20210120T100000
X-MOZ-FAKED-MASTER:1
X-MOZ-GENERATION:1
DURATION:PT1H
CLASS:PUBLIC
END:VEVENT

I've created a patch that works for me. Im ' testing DTEND which is not there because of the nature of the copying.