Get a random post link from WP database using query

gistfile1.php

<?php
function get_random_post_link() {

	$args = array(
		'orderby' => 'rand',
		'posts_per_page' => '1',
		);

	$wp_query = new WP_Query( $args );
	if ( $wp_query->have_posts() ) : while ( $wp_query->have_posts() ) : $wp_query->the_post(); 
	$postlink = get_the_permalink();
	endwhile; endif; wp_reset_query();

	return $postlink; 
}
?>

May I suggest to initialize the $postlink that in case no posts where found you'll get Notice: Undefined variable: postlink in