Ok, but your codes uses $_zp_current_album. So that album apparently exists why the check does not make real sense to me...
The way to check for a toplevel album existing is to use the object model.
`
$albums = $_zp_gallery->getAlbums();
foreach($albums as $album) {
if($album == '<folder name to check>') {
<do something>
}
}
`
Or just try to create the object...if the album is not there it will not work (you can check with $obj->exists btw).