custom post meta html

is there any way to have custom post meta+html not output if the box is blank?

I’m bit of a php newbie and have been reading up on it, but i have tried ‘undefined’ as well as ‘null’. Also tried: if (isset($embed)), but probably did it wrong? None seem to work.

if ($embed != null) {
	echo '<div id="slide"><iframe title="YouTube video player" width="424" height="348" src="https://www.youtube.com/embed/';
	echo get_post_meta($post->ID, "embed", true);
        echo '" frameborder="0" allowfullscreen></iframe></div>';
}

here is portion of functions.php that has the embed code for custom post meta:

add_action('init', 'package_register');

function package_register() {
	$args = array(
    	'label' => __('packages'),
    	'singular_label' => __('package'),
    	'public' => true,
    	'show_ui' => true,
    	'capability_type' => 'post',
    	'hierarchical' => false,
    	'rewrite' => true,
    	'supports' => array('title', 'editor', 'thumbnail')
    );

	register_post_type( 'package' , $args );
}
	add_action("admin_init", "admin_init");
	add_action('save_post', 'save_embed');

	function admin_init(){
		add_meta_box("prodInfo-meta", "package Options", "meta_options", "package", "side", "low");
	}

	function meta_options(){
		global $post;
		$custom = get_post_custom($post->ID);
		$embed = $custom["embed"][0];
		echo '<img src="https://www.address.com/wp-content/themes/slideshow/images/vimeo.png"><br /><label>embed:</label><input type="text" name="embed" value="'. $embed .'" />';
	}

function save_embed(){
	if(isset($_POST["date"]))
	update_post_meta($post->ID, “horario”, $_POST["date"]);
	global $post;
	update_post_meta($post->ID, "embed", $_POST["embed"]);
}
// custom table columns
register_taxonomy("catalog", array("package"), array("hierarchical" => true, "label" => "Catalogs", "singular_label" => "Catalog", "rewrite" => true));

also anyone know if custom post meta can store html? seem to have some issues with it storing html, but alpha-numeric numbers seem to work fine.