display store picker only for users of blog id 1

Hi,

I only want users of blog id (1) to be able to see the global marketpress store selector that is in the header.php of framemarket theme.
Around line 37 of header.php in this pastebin http://pastebin.com/kae77Xvn

I changed

<?php } ?>
<?php if ( is_multisite() ) {?>
<?php
$options = get_option('framemarket_theme_options');
$showpicker = $options['pickerinput'];
if ($showpicker == "Yes"){
?>
<div id="mp-storepicker">

to

<?php } ?>
<?php
global $blog_id;
global $current_user;
get_currentuserinfo();
if (is_blog_user (1) && ( ( is_multisite() ) ) {?>
<?php
and it didn't work, I got a white screen. How do I fix? The error message is

Warning: Cannot modify header information - headers already sent by (output started at wp-includes/functions.php:2628) in wp-includes/pluggable.php on line 881