set default empty message, See #11644

git-svn-id: https://develop.svn.wordpress.org/trunk@12775 602fd350-edb4-49c9-b593-d223f7449a82

wp-admin/includes/schema.php

@@ -622,6 +622,7 @@ function populate_roles_300() {
 function populate_network( $network_id = 1, $domain = '', $email = '', $site_name = '', $path = '/', $vhost = 'no' ) {
 	global $wpdb, $current_site, $wp_version, $wp_db_version, $wp_rewrite;
 
+	$msg = '';
 	//@todo: turn these checks into returned messages
 	if ( $domain == '' )
 		die( 'You must provide a domain name!' );