Revision 17531: 57_Calendar: fix for Perl warning on undefined $t when download of ...

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Revision 17531: 57_Calendar: fix for Perl warning on undefined $t when download of ...

57_Calendar: fix for Perl warning on undefined $t when download of ical has failed; added note on Nextcloud calendar

Source: Revision 17531: 57_Calendar: fix for Perl warning on undefined $t when download of ...