software-properties-gtk crashed with TypeError in new_init(): could not convert value for property `transient_for' from DialogCacheOutdated to GtkWindow

[ivanto]

:~$ lsb_release -rd
Description: Ubuntu 20.04.1 LTS
Release: 20.04

:~$ apt-cache policy software-properties-gtk
software-properties-gtk:
  Installed: 0.98.9.2
  Candidate: 0.98.9.2
  Table version:
 *** 0.98.9.2 500
        500 http://archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages
        500 http://archive.ubuntu.com/ubuntu focal-updates/main i386 Packages
        500 http://archive.ubuntu.com/ubuntu focal-security/main amd64 Packages
        500 http://archive.ubuntu.com/ubuntu focal-security/main i386 Packages
        100 /var/lib/dpkg/status
     0.98.9 500
        500 http://archive.ubuntu.com/ubuntu focal/main amd64 Packages
        500 http://archive.ubuntu.com/ubuntu focal/main i386 Packages

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: software-properties-gtk 0.98.9.2
ProcVersionSignature: Ubuntu 5.4.0-51.56-generic 5.4.65
Uname: Linux 5.4.0-51-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.9
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: LXQt
Date: Wed Oct 14 14:49:36 2020
PackageArchitecture: all
SourcePackage: software-properties
UpgradeStatus: No upgrade log present (probably fresh install)