Problem with Referrer Manual Backup URL disclosure

There is a .css file in backup.php that’s included in the header of the manual backup status page that links to songpane.com

This file isn’t even on their server and results in a 404 error on their website.
The referrer url could be disclosed via analytics (webtracking) software to the operator of the songpane website.

This is the exact link in your source
<link rel="stylesheet" id="install-css" href="https://songpane.com/wp-admin/css/install.css" type="text/css" media="all" />

Just needs to be localized, or preferably gone all together.

https://www.ads-software.com/extend/plugins/backup/

[No bumping, thank you.]