[DAV] Fix time-range filter for all-day events

aleksis/core/util/dav_handler/calendar.py

@@ -30,7 +30,7 @@ class TimeRangeFilter(ElementHandler):
                     filter(
                         lambda obj: self._compare_date_time(d, obj.value_end_datetime(obj))
                         if obj.value_end_datetime(obj) is not None
-                        else True,
+                        else self._compare_date_time(d, obj.value_start_datetime(obj)),
                         self.request.objects,
                     )
                 )