Bug fix suggestion for header image

Hi.
Thanks for the great theme.
I noticed that there is a file type extension typo in /spring-song/functions.php line 54-56.
The code is

register_default_headers(
		array(
			'spring' => array(
				'url'           => '%2$s/images/headers/spring.jpg',
				'thumbnail_url' => '%2$s/images/headers/spring-thumb.jpg',
				/* Translators: Header image description. */
				'description'   => __( 'Spring Song default header', 'spring-song' )
			)
		)
	);

But is should be

register_default_headers(
		array(
			'spring' => array(
				'url'           => '%2$s/images/headers/spring.png',
				'thumbnail_url' => '%2$s/images/headers/spring-thumb.png',
				/* Translators: Header image description. */
				'description'   => __( 'Spring Song default header', 'spring-song' )
			)
		)
	);