Hide uncategorized category from the shop page on the frontend

add_filter( 'woocommerce_product_categories_widget_args', 'remove_uncategorized_category' );
add_filter( 'woocommerce_product_subcategories_args', 'remove_uncategorized_category' );

function remove_uncategorized_category( $args ) {
  $uncategorized = get_option( 'default_product_cat' );
  $args['exclude'] = $uncategorized;
  return $args;
}

* Originally from https://gist.github.com/mikejolley/409a5180632535addb93a2ac63576193#file-functions-php