if ($image_add) {
if (!empty($image_add[0])) {
$image_add_1 = $this->model_tool_image->resize($image_add[0], $this->config->get($this->config->get('config_theme') . '_image_product_width'), $this->config->get($this->config->get('config_theme') . '_image_product_height'));
$image_add_1 = $this->model_tool_image->resize($image_add[0]['image'], $this->config->get($this->config->get('config_theme') . '_image_product_width'), $this->config->get($this->config->get('config_theme') . '_image_product_height'));
thumb_1' => $image_add_1
thumb_1' => isset($image_add_1) ? $image_add_1 : '';
и все это не красиво, лучше как-то так
//Добавление доп изображения -------------------------------->
$image_add = $query = $this->db->query("SELECT `image` FROM " . DB_PREFIX . "product_image WHERE product_id = '" . (int)$result['product_id'] . "' ORDER BY sort_order ASC LIMIT 1")->row;
if (!empty($image_add['image'])) {
$image_add_1 = $this->model_tool_image->resize($image_add['image'], $this->config->get($this->config->get('config_theme') . '_image_product_width'), $this->config->get($this->config->get('config_theme') . '_image_product_height'));
} else {
$image_add_1 = '';
}
// ...
$data['products'][] = array(
'product_id' => $result['product_id'],
'thumb' => $image,
'thumb_1' => $image_add_1,
// ...
З.Ы. Код не проверял, но должно работать.