Gracefully handle caldav event with missing summary (#84719)

fixes undefined

homeassistant/components/caldav/calendar.py

@@ -184,7 +184,7 @@ class WebDavCalendarData:
                 continue
             event_list.append(
                 CalendarEvent(
-                    summary=vevent.summary.value,
+                    summary=self.get_attr_value(vevent, "summary") or "",
                     start=vevent.dtstart.value,
                     end=self.get_end_date(vevent),
                     location=self.get_attr_value(vevent, "location"),
@@ -264,7 +264,9 @@ class WebDavCalendarData:
             return
 
         # Populate the entity attributes with the event values
-        (summary, offset) = extract_offset(vevent.summary.value, OFFSET)
+        (summary, offset) = extract_offset(
+            self.get_attr_value(vevent, "summary") or "", OFFSET
+        )
         self.event = CalendarEvent(
             summary=summary,
             start=vevent.dtstart.value,

tests/components/caldav/test_calendar.py

@@ -214,6 +214,18 @@ DESCRIPTION:The bell tolls for thee
 RRULE:FREQ=HOURLY;INTERVAL=1;COUNT=12
 END:VEVENT
 END:VCALENDAR
+""",
+    """BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//Global Corp.//CalDAV Client//EN
+BEGIN:VEVENT
+UID:14
+DTSTAMP:20151125T000000Z
+DTSTART:20151127T000000Z
+DTEND:20151127T003000Z
+RRULE:FREQ=HOURLY;INTERVAL=1;COUNT=12
+END:VEVENT
+END:VCALENDAR
 """,
 ]
 
@@ -917,7 +929,7 @@ async def test_get_events(hass, calendar, get_api_events):
     await hass.async_block_till_done()
 
     events = await get_api_events("calendar.private")
-    assert len(events) == 14
+    assert len(events) == 15
     assert calendar.call