WooCommerce - Set sale price to regular price

<?php
  // set sale price = regular price if sale price is zero
  // should set sale price to blank?
  // needs additional error checking
  // does not work for direct access to cart page
  // intended as a framework for further development
  // code goes in functions.php for your child theme
  add_action ('woocommerce_before_shop_loop_item', 'check_sale_price', 40 );
  add_action('woocommerce_before_single_product', 'check_sale_price', 40 );
  function check_sale_price() {
        $billing_first_name = get_post_meta(3834, '_billing_first_name', true );
        print $billing_first_name;
    global $product;
    if ( $product->sale_price == '0' ) {
      $price = $product->regular_price;
      $product->sale_price = $price;
      $product->price = $price;
      global $wpdb;
      $wpdb->get_results( 'UPDATE sa_postmeta SET meta_value='.$price.' WHERE meta_key="_sale_price" AND post_id='.$product->id, OBJECT );
      $wpdb->get_results( 'UPDATE sa_postmeta SET meta_value='.$price.' WHERE meta_key="_price" AND post_id='.$product->id, OBJECT );
    }
  }