Updated to 1.7.3 error: Trying to get property of non object

function check_password_lockout($username = '')
    {    
        global $IN, $DB, $PREFS;
        
  if ($PREFS->ini('password_lockout') == 'n')
  {
          return FALSE; 
        } 
        
        if ($PREFS->ini('password_lockout_interval') == '')
        {
          return FALSE; 
        }
        
        $interval = $PREFS->ini('password_lockout_interval') * 60;
        
        $expire = time() - $interval;
  
    $sql = "SELECT count(*) AS count 
      FROM exp_password_lockout 
      WHERE login_date > $expire 
      AND ip_address = '".$DB->escape_str($IN->IP)."'
      AND (user_agent = '".$DB->escape_str($this->userdata['user_agent'])."'
     OR username = '".$DB->escape_str($username)."'
     )";
      
  $query = $DB->query($sql);

  if ($query->row['count'] >= 4)
  {
   return TRUE;
  }
  else
  {
   return FALSE;
  }
    }