Description:
------------
Unserialize shows UNKNOW in result

Test script:
---------------
var_dump(unserialize('a:2:{i:0;O:9:"exception":1:{s:16:"'."\0".'Exception'."\0".'trace";s:4:"test";}i:1;R:3;}'));

Expected result:
----------------
no UNKNOW

Actual result:
--------------
array(2) {
  [0]=>
  object(Exception)#1 (6) {
    ["message":protected]=>
    string(0) ""
    ["string":"Exception":private]=>
    string(0) ""
    ["code":protected]=>
    int(0)
    ["file":protected]=>
    string(10) "/tmp/1.php"
    ["line":protected]=>
    int(2)
    ["trace":"Exception":private]=>
    &UNKNOWN:0
  }
  [1]=>
  &UNKNOWN:0
}