Description:
------------
When creating a DatePeriod object with no end date, but recurrances given, the runtime segfaults.

Test script:
---------------
<?php
// https://3v4l.org/a044v

$period = new DatePeriod(new DateTimeImmutable("now"), new DateInterval("P2Y4DT6H8M"), 2);

var_dump($period->getStartDate());
var_dump($period->getEndDate());

Expected result:
----------------
object(DateTimeImmutable)#2 (3) { 
  ["date"]=> string(26) "2016-02-19 21:45:08.000000"
  ["timezone_type"]=> int(3)
  ["timezone"]=> string(16) "Europe/Amsterdam" 
}
object(DateTimeImmutable)#8 (1) {
  ["date"]=> string(26) "2016-02-19 21:59:23.000000"
  ["timezone_type"]=> int(3)
  ["timezone"]=> string(13) "Europe/Berlin"
}


Actual result:
--------------
object(DateTimeImmutable)#2 (3) { 
  ["date"]=> string(26) "2016-02-19 21:45:08.000000"
  ["timezone_type"]=> int(3)
  ["timezone"]=> string(16) "Europe/Amsterdam" 
}
Process exited with code 139.