MPTtree, Hieararchical trees in a database table

[eluser]Antivanity[/eluser]
I'm having problems with this..

Code:

$this->load->MPTT('user_tree');
$this->user_tree->insert_root(array('title'=>'FAS', 'userid'=>'1'));

PHP Fatal error: Cannot pass parameter 1 by reference in /home/camalotlms.com/system/application/models/mpttree.php on line 405

Heres the function that the error is in..

Code:

function get_root(){
        $query = $this->db->getwhere($this->tree_table,array($this->left_col => 1),1);
        $return = $query->num_rows() ? $query->row_array() : false;
        if(!$return)
            $this->debug_message('Root node was not found.'); // this is like 405 with the error..
        return $return;
    }