Remove Untitled category from the breadcrumb.

woocommerce-remove-uncategorized-from-breadcrumb.php

<?php // don't copy this line in your code.
/**
 * Remove uncategorized from the WooCommerce breadcrumb.
 * 
 * @param  Array $crumbs    Breadcrumb crumbs for WooCommerce breadcrumb.
 * @return Array   WooCommerce Breadcrumb crumbs with default category removed.
 */
function your_prefix_wc_remove_uncategorized_from_breadcrumb( $crumbs ) {
	$category 	= get_option( 'default_product_cat' );
	$caregory_link 	= get_category_link( $category );

	foreach ( $crumbs as $key => $crumb ) {
		if ( in_array( $caregory_link, $crumb ) ) {
			unset( $crumbs[ $key ] );
		}
	}

	return array_values( $crumbs );
}

add_filter( 'woocommerce_get_breadcrumb', 'your_prefix_wc_remove_uncategorized_from_breadcrumb' );