问如何使用辅助器显示来自do_upload的错误消息

EN

   public function edit($id) {
        $this->edit_status_check($id);
        $this->form_validation->set_rules('agent_name', 'Agent Name', 'required');
        $this->form_validation->set_rules('mobile', 'Mobile No.', 'required');
        $this->form_validation->set_rules('agent_vehicle', 'Agent Vehicle', 'required');
        if ($this->form_validation->run() == FALSE) {
            $data = array(
                'page_title' => 'Edit Agent',
                'page_name' => 'agent/edit',
                'result' => $this->agent_model->select_id($id),
                'result_vehicle' => $this->vehicle_model->list_all(),
                'error' => validation_errors(),
                'id' => $id
            );
            $this->load->view('template', $data);
        } else {
            $config['upload_path'] = '../uploads/agent/';
            $config['allowed_types'] = 'jpg|jpeg';
            $config['encrypt_name'] = TRUE;
            $config['max_size'] = 1000; // 1 mb
            $this->load->library('upload', $config);
      if (!empty($_FILES['agent_image']['name'])) {
                if ($this->upload->do_upload('agent_image')) {
                    $_POST['agent_img_url'] = 'uploads/agent/' . $this->upload->data('file_name');
                } else {
                    $data = array(
                        'page_title' => 'Edit Agent',
                        'page_name' => 'agent/edit',
                        'result' => $this->agent_model->select_id($id),
                        'result_vehicle' => $this->vehicle_model->list_all(),
                        'error' => $this->upload->display_errors(),
                        'id' => $id
                    );
                    $this->load->view('template', $data);
                }
            }
            $this->agent_model->update($_POST, $id);
            alert('Update', $_POST['agent_name']);
            redirect('agent');
        }
    }

  public function update($data, $id) {
        $updatedata = array(
            'name' => $data['agent_name'],
            'mobile' => $data['mobile'],
            'password' => sha1($data['password']),
            'vehicle' => $data['agent_vehicle'],
            'address' => $data['agent_address'],
            'category' => $data['category'],
            'created_on' => date('Y-m-d h:i:sa')
        );
        if (!empty($data['agent_img_url'])) {
            $updatedata['img_url'] = $data['agent_img_url'];
        }
        $this->db->where('id', $id);
        $this->db->update('agent', $updatedata);
    }

 <div class="form-group">
                            <img src="/<?= $result['img_url']; ?>" class="img-responsive" name="old_agent_image" width="133" height="100">
                        </div>
                        <div class="form-group">
                            <label>Agent Image</label>
                            <input type="file" name="agent_image">
                        </div>