DB/Query Error

[eluser]Shujin[/eluser]

Code:

function is_staff()
    {
        $id = $this->ci->session->userdata('userid');
        $query = $this->ci->db->get_where('group_memberships', array('userid' => $id));
        $group = $query->row()->groupid;
        
        if ($group <= 2) {
            return true;
        }
    }

Which seems to give me this error:

A PHP Error was encountered

Severity: Notice

Message: Trying to get property of non-object

Filename: libraries/quickauth.php

Line Number: 184

But I have the exact same code right above (at Line: 173)
but it only detects the error at this line.