$this->config in model breaks Output.php

[eluser]Crafter[/eluser]
Use of a local class variable $config breake /system/libraries/Output.php.
(suspect same for controllers etc)

To reproduce:

1. Step 1 : Create model

Code:

class MyModel extends Model {

var $config;

   function GalleryModel()
   {
      parent::Model();
      $this->obj =& get_instance();

      $this->config = '';

   }
}

2. Step 2. Create model instamce (in controller)

Code:

$this->load->model('mymodel');

Ouput.php breaks here (when trying to invole global $CFG

Code:

// Is compression requested?
                if ($CFG->item('compress_output') === TRUE)
                {
                        if (extension_loaded('zlib'))
                        ...
                 }

Thank you.