Removing 'portfolio-view' from url – almost what is missing from code?

I am trying to remove portfolio view from url and followed instructions to remove its name from highlighted section. This works but has left me with ‘portfolio’ now even though field is blank. what is wrong with this code or need changing in breadcrumbs please?
trying to get:
https://www.sitename.com/post
currently have: http//www.sitename.com/portfolio/post

/* Portfolio */
function my_post_type_portfolio() {
	register_post_type( 'portfolio',
                array(
				'label' => __('Portfolio'),
				'singular_label' => __('Porfolio Item', 'theme'),
				'_builtin' => false,
				'public' => true,
				'show_ui' => true,
				'show_in_nav_menus' => true,
				'capability_type' => 'page',
				'menu_icon' => get_template_directory_uri() . '/includes/images/icon_portfolio.png',
				<strong>'rewrite' => array(
					'slug' => '',
					'with_front' =>false,</strong>
				),
				'supports' => array(
						'title',
						'editor',
						'thumbnail',
						'excerpt',
						'custom-fields',
						'comments')
					)
				);
	register_taxonomy('portfoliocat', 'portfolio', array('hierarchical' => true, 'label' => 'Portfolio Categories', 'singular_name' => 'Category', "rewrite" => true, "query_var" => true));
}

add_action('init', 'my_post_type_portfolio');

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