[horde] Turba: Fatal Error because of config file

[Jan Niggemann]

Hi list,

when I try to configure turba, I get a fatal error: "Call to a member  
function hasChildNodes() on null"

Debugging shows that this is because of the file  
.../turba/config/conf.d/10-webmail.xml.

The files content is exactly like this:
https://raw.githubusercontent.com/horde/horde/master/bundles/webmail/turba/config/conf.d/10-webmail.xml

Observations:
- Renaming the conf.d directory to something else makes the error go away
- Everything seems to work normally

What is this file for, can I safely delete it?
Otherwise I'd rename the conf.d directory, configure turba, and then  
re-rename it to conf.d...

This is on a H5 (Horde Groupware Webmail Edition 5.2.4), turba 4.2.4  
and Horde 5.2.3...

JanN