_recordsFromQuery should return empty tuple if query is None


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@13885 e27351fd-9f3e-4f54-a53b-843176b1656c
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git-svn-id: https://svn.calendarserver.org/repository/calendarserver@13886 e27351fd-9f3e-4f54-a53b-843176b1656c