Continuie button is missing in Oscommerce

Add the below code BEFORE "if (isset($navigation->path[$back])) {" in the shopping_cart.php
// BOF FWR Mod category based continue button
        $count = count($products);
        if( isset($products[$count-1]['id']) ) {
          $continueButtonId = tep_get_product_path(str_replace(strstr($products[$count-1]['id'], '{'), '', $products[$count-1]['id']));
        }
        if( isset($continueButtonId) ) {
?>
                                <td align="center" class="main"><?php echo '<a href="' . tep_href_link(FILENAME_DEFAULT, 'cPath=' . $continueButtonId) . '">' . tep_image_button('button_continue_shopping.gif', IMAGE_BUTTON_CONTINUE_SHOPPING) . '</a>'; ?></td>
<?php
    //if (isset($navigation->path[$back])) {
        } else