Error invalid argument supplied for foreach() dalam codeigniter

saya mau bertanya mengenai error error Invalid argument supplied for foreach() dengan source code berikut:

controllernya: public function detail($id_invoice){ $data['invoice'] = $this->model_invoice->ambil_id_invoice($id_invoice); $data['pesanan'] = $this->model_invoice->ambil_id_pesanan($id_invoice); //var_dump($data2); $this->load->view('templates_admin/header'); $this->load->view('templates_admin/sidebar'); $this->load->view('admin/detail_invoice',$data); $this->load->view('templates_admin/footer'); }

modelnya: public function ambil_id_pesanan($id_invoice) { $result = $this->db->where('id_invoice',$id_invoice)->get('tb_pesanan'); if($result->num_rows() > 0){ return $result->result(); }else{ return false; } }

viewsnya: jumlah*$psn->harga; $total += $subtotal; ?>

id_brg ?> nama_brg ?> jumlah ?> harga,0,',','.') ?>

dan selalu error seperti berikut: A PHP Error was encountered Severity: Warning Message: Invalid argument supplied for foreach()