Description:
------------
When returning an array element from a function by reference, if the element key does not exist, the element key is added.

Reproduce code:
---------------
class simple
{
	var $items = array();
	
	function &getItem($name)
	{
		return $this->items[$name];
	}
}

$obj = new simple();

print "Keys before getting item:\n".print_r(array_keys($obj->items), TRUE)."\n";

$retrieved =& $obj->getItem('SHOULD_NOT_EXIST');

print "Retrieved: \n";
var_dump($retrieved);

print "Keys after getting item:\n".print_r(array_keys($obj->items), TRUE)."\n";

Expected result:
----------------
Keys before getting item:
Array
(
)

Retrieved: 
NULL
Keys after getting item:
Array
(
)


Actual result:
--------------
Keys before getting item:
Array
(
)

Retrieved: 
NULL
Keys after getting item:
Array
(
    [0] => SHOULD_NOT_EXIST
)