Description:
------------
I've tryed to create the MessageFormatter class, from intl extension, 
passing an empty string for the constructor's second argument and I was 
pretty surprised to get NULL instead of object instance :)

Reproduce code:
---------------
$f = new MessageFormatter(Locale::getDefault(), '');
var_dump($f, is_object($f));

$f = MessageFormatter::create(Locale::getDefault(), '');
var_dump($f, is_object($f));


Expected result:
----------------
object(MessageFormatter)#1 (0) {
}
bool(true)
object(MessageFormatter)#2 (0) {
}
bool(true)

Actual result:
--------------
NULL
bool(false)
NULL
bool(false)