WordPress Multisite Wide

I tried it on a simple multisite setup as a prototype. There is a problems with the permalinks on the main page, but I managed to make a workaround, so that the guid is stored instead of the permalink on the main page.
You have to change the mss_build_document function in “advanced-search-by-my-solr-server.inc.php” on line 206

change from

$doc->setField( 'permalink', get_permalink( $post_info->ID ) );

to

$permalink = "";
if(is_main_site()){
   $permalink = $post_info->guid;
} else {
   $permalink = get_permalink( $post_info->ID );
}
$doc->setField( 'permalink', $permalink );