GLib's GResource files are mismatched as application/vnd.recordare.musicxml+xml
XML files used across GLib and GTK projects are being mismatched as a music xml format, giving us the wrong icons.
A quick example:
<?xml version="1.0" encoding="UTF-8"?>
<gresources>
<gresource path="/foo">
</gresource>
</gresources>