Description:
------------
Caught exception assignment to variables ignores references.
Note that PHP has this bug while HHVM hasn't.

Test on 3v4l: https://3v4l.org/neGAE

Test script:
---------------
<?php

$var = null;
$e = &$var;

try {
    throw new Exception;
} catch (Exception $e) { }

assert('$e !== null');
assert('$var !== null');

Expected result:
----------------
No outputs.

Actual result:
--------------
Warning: assert(): Assertion "$var !== null" failed