Kolourpaint: No tool icons after upgrade 20.04 -> 20.10

- Install Kolourpaint on 20.04.
- Upgrade system from XUbuntu 20.04 to 20.10.
- Open Kolourplaint
- EXPECTED: Icons are shown in the "tools" bar to the left.
- ACTUAL: Only text is shown in the "tools" bar to the left.

I veryfied this on two different systems.

lsb_release -rd
===================
Description: Ubuntu 20.10
Release: 20.10

apt-cache policy pkgname kolourpaint
=====================================
kolourpaint:
  Installed: 4:20.08.1-0ubuntu1
  Candidate: 4:20.08.1-0ubuntu1
  Version table:
 *** 4:20.08.1-0ubuntu1 500
        500 http://archive.ubuntu.com/ubuntu groovy/universe amd64 Packages
        100 /var/lib/dpkg/status
N: Unable to locate package pkgname
nimono@nimono:~$

ProblemType: Bug
DistroRelease: Ubuntu 20.10
Package: kolourpaint 4:20.08.1-0ubuntu1
ProcVersionSignature: Ubuntu 5.8.0-26.27-generic 5.8.14
Uname: Linux 5.8.0-26-generic x86_64
ApportVersion: 2.20.11-0ubuntu50
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: XFCE
Date: Mon Nov 9 07:45:02 2020
SourcePackage: kolourpaint
UpgradeStatus: No upgrade log present (probably fresh install)