function verify_username_password( $user, $username, $password ) {
$login_page  = home_url( '/login/' );
if( $username == "" || $password == "" ) {
    wp_redirect( $login_page . "?login=empty" );
    exit;
  }
}
add_filter( 'authenticate', 'verify_username_password', 1, 3);

if (is_super_admin()) {
header('Location: wp-admin.php');
}
else {
header('Location: index.php');
}