khelpcenter shows error instead of UNIX manual pages

[Norbert]

Steps to reproduce:
1. Install KHelpCenter
2. Open KHelpCenter
3. Navigate to UNIX manual pages

Expected results:
* KHelpCenter show UNIX manual pages

Actual results:
* KHelpCenter renders error page:

The requested operation could not be completed
Cannot Initiate the man Protocol
Technical Reason: Unable to Launch Process

Details of the Request:
URL: man:/
Protocol: man
Date and Time: вторник, 24 июля 2018 г. 14:44:26 MSK
Additional Information: Cannot talk to klauncher: The name org.kde.klauncher5 was not provided by any .service files
Description:
The program on your computer which provides access to the man protocol could not be started. This is usually due to technical reasons.
Possible Causes:
The program which provides compatibility with this protocol may not have been updated with your last update of KDE. This can cause the program to be incompatible with the current version and thus not start.
You may have encountered a bug in the program.
Possible Solutions:
Update your software to the latest version. Your distribution should provide tools to update your software.
Contact your appropriate computer support system, whether the system administrator, or technical support group for further assistance.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: khelpcenter 4:5.5.5-0ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-130.156-generic 4.4.134
Uname: Linux 4.4.0-130-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
CurrentDesktop: MATE
Date: Tue Jul 24 14:39:36 2018
InstallationDate: Installed on 2018-01-04 (200 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
SourcePackage: khelpcenter
UpgradeStatus: No upgrade log present (probably fresh install)