Fix customized timezone guesser (#63)

lib/TimezoneGuesser/GuessFromCustomizedTimeZone.php

@@ -21,18 +21,29 @@ public function guess(VTimeZone $vtimezone, bool $failIfUncertain = false): ?Dat
  $timezones = DateTimeZone::listIdentifiers();
  $standard = $vtimezone->STANDARD;
  $daylight = $vtimezone->DAYLIGHT;
+ if (!$standard) {
+ return null;
+ }
+
+ $standardOffset = $standard->TZOFFSETTO;
+ if (!$standardOffset) {
+ return null;
+ }
+ $standardOffset = $standardOffset->getValue();
 
- $standardOffset = $standard->TZOFFSETTO->getValue();
- $standardRRule = $daylight ? $standard->RRULE->getValue() : 'FREQ=DAILY';
+ $standardRRule = $standard->RRULE ? $standard->RRULE->getValue() : 'FREQ=DAILY';
  // The guess will not be perfectly matched since we use the timezone data of the current year
  // It might be wrong if the timezone data changed in the past
  $year = (new DateTimeImmutable('now'))->format('Y');
  $start = new DateTimeImmutable($year . '-01-01');
  $standardIterator = new RRuleIterator($standardRRule, $start);
  $standardIterator->next();
 
+ if ($daylight && !$daylight->TZOFFSETTO) {
+ $daylight = null;
+ }
  $daylightOffset = $daylight ? $daylight->TZOFFSETTO->getValue() : '';
- $daylightRRule = $daylight ? $daylight->RRULE->getValue() : '';
+ $daylightRRule = $daylight ? ($daylight->RRULE ? $daylight->RRULE->getValue() : 'FREQ=DAILY') : '';
  $daylightIterator = $daylight ? new RRuleIterator($daylightRRule, $standardIterator->current()) : null;
  $daylightIterator && $daylightIterator->next();
 

tests/VObject/TimeZoneUtilTest.php

@@ -625,7 +625,7 @@ public function testCustomizedTimeZoneWithoutDaylight()
  {
  $ics = $this->getCustomizedICS();
  $tz = TimeZoneUtil::getTimeZone('Customized Time Zone', Reader::read($ics));
- $this->assertNotSame('Customized Time Zone', $tz->getName());
+ $this->assertSame('Asia/Brunei', $tz->getName());
  $start = new \DateTimeImmutable('2022-04-25');
  $this->assertSame(8 * 60 * 60, $tz->getOffset($start));
  }