CI session library BUG?

[eluser]vps4[/eluser]
/* Location: ./system/libraries/Session.php */
line: 270-282

Code:

if (count($custom_userdata) === 0)
        {
            $custom_userdata = '';
        }
        else
        {
            // Serialize the custom data array so we can store it
            $custom_userdata = $this->_serialize($custom_userdata);
        }

        // Run the update query
        $this->CI->db->where('session_id', $this->userdata['session_id']);
        $this->CI->db->update($this->sess_table_name, array('last_activity' => $this->userdata['last_activity'], 'user_data' => $custom_userdata));

AND http://ellislab.com/codeigniter/user-gui...sions.html

Code:

CREATE TABLE IF NOT EXISTS  `ci_sessions` (
session_id varchar(40) DEFAULT '0' NOT NULL,
ip_address varchar(16) DEFAULT '0' NOT NULL,
user_agent varchar(50) NOT NULL,
last_activity int(10) unsigned DEFAULT 0 NOT NULL,
user_data text NOT NULL,
PRIMARY KEY (session_id)
);

the bug is:

Code:

user_data text NOT NULL

when

Code:

$custom_userdata = '';

this line will get error:

Code:

$this->CI->db->update($this->sess_table_name, array('last_activity' => $this->userdata['last_activity'], 'user_data' => $custom_userdata));

How can I fix it?
change database table to :

Code:

user_data text NULL

OR modify
/* Location: ./system/libraries/Session.php */
like:

Code:

if (count($custom_userdata) === 0)
        {
            $custom_userdata = '';
                        return false;
        }