JezK

Edit File: product-image.php

<?php
/**
 * Single Product Image
 *
 * This template can be overridden by copying it to yourtheme/woocommerce/single-product/product-image.php.
 *
 * HOWEVER, on occasion WooCommerce will need to update template files and you
 * (the theme developer) will need to copy the new files to your theme to
 * maintain compatibility. We try to do this as little as possible, but it does
 * happen. When this occurs the version of the template file will be bumped and
 * the readme will list any important changes.
 *
 * @see     https://docs.woocommerce.com/document/template-structure/
 * @package WooCommerce/Templates
 * @version 3.5.1
 */

defined( 'ABSPATH' ) || exit;

// Note: `wc_get_gallery_image_html` was added in WC 3.3.2 and did not exist prior. This check protects against theme overrides being used on older versions of WC.
if ( ! function_exists( 'wc_get_gallery_image_html' ) ) {
	return;
}

global $product;

$columns           = apply_filters( 'woocommerce_product_thumbnails_columns', 4 );
$post_thumbnail_id = $product->get_image_id();
$wrapper_classes   = apply_filters( 'woocommerce_single_product_image_gallery_classes', array(
	'woocommerce-product-gallery',
	'woocommerce-product-gallery--' . ( $product->get_image_id() ? 'with-images' : 'without-images' ),
	'woocommerce-product-gallery--columns-' . absint( $columns ),
	'images',
) );
$attachment_ids    = $product->get_gallery_image_ids();
if(!$attachment_ids){
	$wrapper_classes[]='gallery-without-thumb';
}
$thumb_images='';
$gallery_layout=zoo_product_gallery_layout();
?>
<div class="<?php echo esc_attr( implode( ' ', array_map( 'sanitize_html_class', $wrapper_classes ) ) ); ?>"
     data-columns="<?php echo esc_attr( $columns ); ?>">
    <figure class="woocommerce-product-gallery__wrapper">
        <div class="wrap-main-product-gallery">
			<?php
			if ( $product->get_image_id() ) {
				$html = wc_get_gallery_image_html( $post_thumbnail_id, true );
			} else {
				$html = '<div class="woocommerce-product-gallery__image--placeholder">';
				$html .= sprintf( '<img src="%s" alt="%s" class="wp-post-image" />', esc_url( wc_placeholder_img_src( 'woocommerce_single' ) ), esc_html__( 'Awaiting product image', 'woocommerce' ) );
				$html .= '</div>';
			}

echo apply_filters( 'woocommerce_single_product_image_thumbnail_html', $html, $post_thumbnail_id );
			$thumb_images.=apply_filters('woocommerce_single_product_image_thumbnail_html', wc_get_gallery_image_html($post_thumbnail_id), $post_thumbnail_id);

if ( $attachment_ids && $product->get_image_id() ) {
				foreach ( $attachment_ids as $attachment_id ) {
					echo apply_filters( 'woocommerce_single_product_image_thumbnail_html', wc_get_gallery_image_html( $attachment_id, true ), $attachment_id );
					$thumb_images.=apply_filters('woocommerce_single_product_image_thumbnail_html', wc_get_gallery_image_html($attachment_id), $attachment_id);
				}
			}
			?>
        </div>
		<?php
		if ( $attachment_ids) {
			if ( $gallery_layout != 'grid' && $gallery_layout != 'slider'&& $gallery_layout != 'sticky') {
				echo sprintf(' <div class="wrap-list-thumbnail">%s</div>',$thumb_images);
			}
		}
		?>
    </figure>
</div>