Stop sending "processing order" e-mail when WooCommerce order status changes from pending to on-hold

functions.php

<?php
/**
 * Disable action that sends e-mail to customer, warning that his/her order is processing,
 * as this is not true, because when the status changes from pending to on-hold,
 * the order is not processing yet.
 *
 * @return 	void
 */
function manipulate_woocommerce_email_sending($email_class){
	remove_action('woocommerce_order_status_pending_to_on-hold_notification', array($email_class->emails['WC_Email_Customer_Processing_Order'], 'trigger'));
	add_action('woocommerce_order_status_on-hold_to_processing_notification', array($email_class->emails['WC_Email_Customer_Processing_Order'], 'trigger'));
}
add_action('woocommerce_email', 'manipulate_woocommerce_email_sending');