404 Background because of wrong parameter

Hey there,

I mentioned out that there is little bug within ultimate-maintenance-mode/template/maintenancemode.php:

The line $url = home_url().'/?mshot='+$pass; will just return int(0), because the pass can’t be math added to the string url.
Following line works perfect:
$url = home_url().'/?mshot='.$pass;

Is it just a mistake or is my webserver doing some fancy stuff here?
Without this change (plus to dot) the mshot-url is just “0” and not “www.xy.z/…” and therefore the background will stay 404.

https://www.ads-software.com/plugins/ultimate-maintenance-mode/