The ETKRootVirtualURIMapping is used in '/modules/adminInterface/virtualURIMapping/default' and set to this property by the ETKModuleVersionHandler:

private CheckAndModifyPropertyValueTask setDefaultVirtualURIMapping = new CheckAndModifyPropertyValueTask("ETK default virtual uri mapping", "", "config", "/modules/adminInterface/virtualURIMapping/default", "class", DefaultVirtualURIMapping.class.getName(), ETKRootVirtualURIMapping.class.getName());

But the ETKRootVirtualURIMapping makes only sense on a author system, and not on a public.
Therefore it should only be set to the property by the VersionHandler on a author system.