fix: handle timezones with no transitions properly

[SebastianKrupinski]

Resolves: https://github.com/nextcloud/calendar/issues/6476

Testing: See issue ticket for details.

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[miaulalala]

Can you elaborate why skipping the first (or 0 position) solves the issue please? :pray:

[SebastianKrupinski]

Can you elaborate why skipping the first (or 0 position) solves the issue please? 🙏

Morning, sure,

This code actually process the first position, instead of skipping it, the original code, skipped transition 0, which in certain time zones is needed for time zones with static transitions.

Here is a example of how Mexico City time zone was being generated:

Before:

BEGIN:VTIMEZONE
TZID:America/Mexico_City
X-MICROSOFT-CDO-TZID:37
END:VTIMEZONE

After:

BEGIN:VTIMEZONE
TZID:America/Mexico_City
X-MICROSOFT-CDO-TZID:37

BEGIN:STANDARD
TZOFFSETFROM:-0600
TZOFFSETTO:-0600
TZNAME:CST
DTSTART:19700101T000000
END:STANDARD

END:VTIMEZONE

The Mexico City timezone has a single static transition which was being skipped originally, and because the "BEGIN:STANDARD" was missing the timezone was never applied to the event, showing the event off by the amount of the timezone offset.

[SebastianKrupinski]

/backport to stable4.7

[st3iny]

/backport to stable5.0