Warning Message in Dashboard

Hello,

I installed wordpress 4.0 on my webserver. I am currently programming my own theme, but an error displays in the backend. This is the message:

Warning: Cannot modify header information – headers already sent by (output started at /home/kajen/public_html/home/wp-content/themes/mytheme/functions.php:2) in /home/kajen/public_html/home/wp-includes/option.php on line 750

Warning: Cannot modify header information – headers already sent by (output started at /home/kajen/public_html/home/wp-content/themes/mytheme/functions.php:2) in /home/kajen/public_html/home/wp-includes/option.php on line 751

The code in my functions.php is:

<?
	if ( function_exists('register_sidebars') )
		register_sidebar(array(
			'before_widget' => '<div id="%1$s" class="widget %2$s">',
			'after_widget' => '</div>',
		));
?>

<?

	add_action( 'init', 'register_my_menus' );

	function register_my_menus() {
		register_nav_menus(
			array(
				'primary-menu' => __( 'Primary Menu' ),
				'secondary-menu' => __( 'Secondary Menu' ),
				'tertiary-menu' => __( 'Tertiary Menu' )
			)
		);
	}

?>

What is wrong? Any suggestions?