ADD review start on product grid by default

I’m using this code to display rating option if the product does not any rating and reviews like all stars in grey color in order to give rating in child theme -> functions.php

remove_action( 'woocommerce_after_shop_loop_item_title', 'woocommerce_template_loop_rating', 5 );
add_action('et_after_shop_loop_title', 'get_star_rating' );
function get_star_rating()
{
    global $woocommerce, $product;
    $average = $product->get_average_rating();

    echo '<div class="star-rating"><span style="width:'.( ( $average / 5 ) * 100 ) . '%"><strong itemprop="ratingValue" class="rating">'.$average.'</strong> '.__( 'out of 5', 'woocommerce' ).'</span></div>';
}

but still i’m not able to see the review grey starts.