paprefs crashes when attempting to select network access

When I go in 'paprefs' to either one of the two network tabs, then all is grayed out (see attached screenshot), and on the right side of each row, it tells 'Installieren ...' (German locale, in English it means 'install'.

What I report here are two things:

The one thing is that it crashes:

When I click on that 'Installieren ...' (it changes to be a button once the mouse is over it), the application crashes, and there is this message on the console from which I startet paprefs:

(paprefs:8331): glibmm-ERROR **: 21:17:31.596:
unhandled exception (type std::exception) in signal handler:
what: basic_string::_M_construct null not valid

The other thing is that it is not possible to use pulse audio over the network, since the checkboxes are grayed out.

Further information:

I expected that there were checkboxes, which I can click on, and than pulse audio would work over network, which I can't since the checkboxes are grayed out.

wind:~ $ lsb_release -rd
Description: Ubuntu Focal Fossa (development branch)
Release: 20.04

wind:~ $ apt-cache policy pulseaudio
pulseaudio:
  Installiert: 1:13.99.1-1ubuntu2
  Installationskandidat: 1:13.99.1-1ubuntu2
  Versionstabelle:
 *** 1:13.99.1-1ubuntu2 500
        500 http://de.archive.ubuntu.com/ubuntu focal/main amd64 Packages
        100 /var/lib/dpkg/status

I just did all updates (apt-get updates ; apt-get dist-upgrade).

I have not done any special settings with audio.
I use Pulse Audio Networking on the same computer with Ubuntu 18.04, and it works there.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: paprefs 1.1-1build1
ProcVersionSignature: Ubuntu 5.4.0-21.25-generic 5.4.27
Uname: Linux 5.4.0-21-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.11-0ubuntu26
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Wed Apr 15 21:12:54 2020
InstallationDate: Installed on 2020-04-03 (11 days ago)
InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Beta amd64 (20200402)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: paprefs
UpgradeStatus: No upgrade log present (probably fresh install)
modified.conffile..etc.default.apport:
 # set this to 0 to disable apport, or to 1 to enable it
 # you can temporarily override this with
 # sudo service apport start force_start=1
 enabled=0
mtime.conffile..etc.default.apport: 2020-04-03T23:24:20.272077