codeigniter - upload image display error if image field is empty

I have this function in my controller. If I add an image, it works fine, but if I don't upload an image, I get the following error:

Message: Undefined index: categoryphoto Filename: controllers/faqcategories.php Line number:90

Here is my code

 public function addNewFaqCategory() 
    {    
        $currentUser = $this->isLoggedIn();
        $this->load->library('upload');
        $this->load->library('form_validation');
        $this->form_validation->set_rules('categoryname', 'Category Name', 'trim|required|xss_clean');
        $this->form_validation->set_rules('categoryname_en', 'Category Name', '');
        $this->form_validation->set_rules('visible', 'Visible', 'trim|required|xss_clean');
        $this->form_validation->set_rules('sorder', 'Sort Order', 'trim|numeric|xss_clean');

        if ($this->form_validation->run() == FALSE) 
        {
            $this->displayAddFaqCategoryForm();
        } else {

            $insertWhat = array(
                                'categoryname'    => $this->input->post('categoryname'),
                                'categoryname_en' => $this->input->post('categoryname_en'),
                                'parentid'        => $this->input->post('parentid'),
                                'description'     => $this->input->post('description'),
                                'description_en'  => $this->input->post('description_en'),
                                'metatags'        => $this->input->post('metatags'),
                                'metatags_en'     => $this->input->post('metatags_en'),
                                'sorder'          => $this->input->post('sorder'),
                                'visible'         => $this->input->post('visible'),
                                'categoryphoto'   => ($_FILES['categoryphoto']['name']) // line 90, error is here....

                               );

            if($insertWhat['categoryphoto'] !="")
            {
                $insertWhat['categoryphoto'] = str_replace(' ', '_',$insertWhat['categoryphoto']);
                $now = date('Y-m-d-His');
                $insertWhat['categoryphoto'] = $now.$insertWhat['categoryphoto'];
        $config['upload_path'] = 'backOffice/backOfficeImages';
        $config['allowed_types'] = 'gif|jpg|jpeg|bmp|png';
        $config['max_size'] = '2048';
        $config['max_width']  = '1024';
        $config['max_height']  = '768';
                $config['file_name'] = $insertWhat['categoryphoto'];
                $this->load->library('upload', $config);
                $this->upload->initialize($config);   
            }
            $this->upload->do_upload('categoryphoto');
            $data = array('upload_data' => $this->upload->data('categoryphoto'));
            $this->load->model('faqcategoriesmodel');
            $this->faqcategoriesmodel->save($insertWhat);
            $this->displayAllFaqCategories();
        }
    } // end of function addNewFaqCategory

Line 90 = 'categoryphoto' => ($_FILES['categoryphoto']['name'])

Any help will be deeply appreciated.

Zoran

You are creating that array before checking the upload, so it will error out if there is no photo uploaded. You should move the array creation after checking/doing the upload

As a one line fix for your code, use this in place of the faulty line:

'categoryphoto'   => isset($_FILES['categoryphoto']['name'])? $_FILES['categoryphoto']['name'] : ''