COUNT in RRULE must be a positive integer

[mkrecek234]

I setup a recurring event which repeats forever, yearly, every 4th Saturday of April.

This event stores properly.
If I edit it in Mac Calendar.app (macOS) and do whatever, it seems the event is adjusted to include COUNT=0.
sabreDAV then will throw an internal error:
COUNT in RRULE must be a positive integer

<d:error xmlns:d="DAV:" xmlns:s="http://sabredav.org/ns">
<s:exception>Sabre\VObject\InvalidDataException</s:exception>
<s:message>COUNT in RRULE must be a positive integer!</s:message>
</d:error>

COUNT=0 should be allowed though for endless events. Even if it does not make sense, it is created in macOS calendar and should not break sabeDAV with internal error.

P.S. Do not get any error adding/changing such entry on other CalDAV servers like used in SOgo etc.