fix: VTODO with only COMPLETED must not crash on time-range check

When a VTODO has COMPLETED but no DTSTART, DUE, or CREATED, the VTODO
branch set comp_end from COMPLETED but left comp_start=None.  The
existing 'if comp_end and not comp_start' guard runs before COMPLETED is
checked, so it did not fire.  Add a second guard after the
CREATED/COMPLETED block to mirror comp_start = comp_end in that case.

Test parametrized over with/without RRULE, as an RRULE-only VTODO
without DTSTART (valid per RFC 5545 §3.6.2) hit a separate KeyError in
xandikos when attempting server-side RRULE expansion.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: tobixen

src/icalendar_searcher/filters.py

@@ -107,6 +107,9 @@ def _check_range(
                     comp_start = _normalize_dt(component["CREATED"].dt)
                 if "COMPLETED" in component:
                     comp_end = _normalize_dt(component["COMPLETED"].dt)
+            ## COMPLETED may have set comp_end while comp_start is still None
+            if comp_end and not comp_start:
+                comp_start = comp_end
 
             ## * A task may have a DUE before the DTSTART.  The
             ##   complicated OR-logic in the table may be eliminated
@@ -159,7 +162,9 @@ def _check_completed_filter(
             pre-resolved value from check_component() to avoid mutating self.
         :return: True if the component should be included, False if it should be filtered out
         """
-        include_completed = _include_completed if _include_completed is not None else self.include_completed
+        include_completed = (
+            _include_completed if _include_completed is not None else self.include_completed
+        )
         if include_completed:
             return True
 

tests/test_check_component.py

@@ -179,3 +179,27 @@ def test_yule_tree2() -> None:
             searcher.add_property_filter(*prop_filter)
             assert not searcher._check_property_filters(cal.subcomponents[0])
             assert not searcher.check_component(cal)
+
+
+@pytest.mark.parametrize("rrule", [None, "RRULE:FREQ=DAILY\n"])
+def test_vtodo_no_dtstart_range_check(rrule: str | None) -> None:
+    """
+    A VTODO with no DTSTART/DUE/CREATED must not crash on a time-range search,
+    whether or not it has an RRULE.
+    """
+    rrule_line = rrule or ""
+    data = f"""BEGIN:VCALENDAR
+VERSION:2.0
+BEGIN:VTODO
+COMPLETED:20231001T105204Z
+DTSTAMP:20231001T124832Z
+{rrule_line}STATUS:COMPLETED
+SUMMARY:g\xe5 tur
+UID:d432d0a2-6058-11ee-97c8-982cbcdd642c
+END:VTODO
+END:VCALENDAR"""
+    cal = Calendar.from_ical(data)
+    end = datetime(2026, 5, 28, 0, 0, 0)
+    searcher = Searcher(todo=True, end=end, include_completed=True)
+    result = searcher.check_component(cal)
+    assert bool(result)