All widget view does not work ( STRG+ F9)

STRG + F9 ( CTRL + F9 ) Enables or disables a view with all widgets. This does not work in Ubuntu.

Error whent started in x-.term:

WARNING: Could not find all icon sizes for the application icon

That's it.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: zim 0.72.0-1
ProcVersionSignature: Ubuntu 5.4.0-47.51-generic 5.4.55
Uname: Linux 5.4.0-47-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.9
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: MATE
Date: Thu Oct 15 22:28:02 2020
InstallationDate: Installed on 2020-09-16 (28 days ago)
InstallationMedia: Ubuntu-MATE 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=de_DE
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: zim
UpgradeStatus: No upgrade log present (probably fresh install)