Font management does not ask for elevated rights when disabling fonts; fails instead

[Bzzz]

Opened via konsole "sudo systemsettings5"

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: systemsettings 4:5.12.4-0ubuntu1
ProcVersionSignature: Ubuntu 4.13.0-41.46~16.04.1-generic 4.13.16
Uname: Linux 4.13.0-41-generic x86_64
NonfreeKernelModules: zfs zunicode zavl zcommon znvpair
ApportVersion: 2.20.9-0ubuntu7
Architecture: amd64
CurrentDesktop: KDE
Date: Fri May 18 22:22:15 2018
InstallationDate: Installed on 2012-06-08 (2170 days ago)
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
SourcePackage: systemsettings
UpgradeStatus: Upgraded to bionic on 2016-04-24 (754 days ago)