A PHP Error was encountered

A PHP Error was encountered 

Severity: Notice 

Message: Only variable references should be returned by reference 

Filename: core/Common.php 

Line Number: 257 

There's a bug with FuelCMS 1.2.1 on PHP 5.6...

A PHP Error was encountered
Severity: Notice
Message: Only variable references should be returned by reference
Filename: core/Common.php
Line Number: 257

Screenshot: http://i.imgur.com/rDFblff.png

Solution 1:

"fuel\codeigniter\core\Common.php"
<return $_config[0] =& $config;
>$_config[0] =& $config;
>return $_config[0];

Solution 2:
Update CodeIgniter from 2.2.0 to 2.2.1.
https://github.com/bcit-ci/CodeIgniter