codeigniter - Mysql: Invalid argument supplied for foreach()

Code:
function countSv_AV_total(){



    $this->db->flush_cache();

    $this->db->start_cache();



   $sql = "select Verzekeringen.naam,\n"

    . " count(*) total,\n"

    . " sum(case when (Age <= 18) then 1 else 0 end) Age18,\n"

    . " sum(case when (Age BETWEEN 19 AND 30) then 1 else 0 end) Age19,\n"

    . " sum(case when (Age BETWEEN 31 AND 50) then 1 else 0 end) Age30,\n"

    . " sum(case when (Age BETWEEN 51 AND 69) then 1 else 0 end) Age50,\n"

    . " sum(case when (Age >= 70) then 1 else 0 end) Age70\n"

    . " from customers\n"

    . " INNER JOIN Verzekeringen\n"

    . " ON customers.AV=Verzekeringen.verzekeringcode\n"

    . " AND Label =1\n"

    . " group by Verzekeringen.naam LIMIT 0, 30 ";



$this->db->query($sql);



    echo $this->db->last_query().'<br />';



    return $this->db->count_all_results('customers','Verzekeringen');

    $this->db->flush_cache();



}