gespeaker crashes upon startup after not finding language "german"

I installed gespeaker to test espeak-ng (with espeak-ng-espeak).
espeak works on the command line with the default German language.

Starting gespeaker didn't give me an application window, so I tried it in the terminal, and got:

loading available plugins...
[DBUS]: init plugin v.0.2
[Debug]: init plugin v.0.2
[Debug]: __init__("Debug", "0.2", "Fabio Castelli", "Debug interface", "/usr/share/gespeaker/plugins/plugin_debug/icon.svg", "")
[Stop on quit]: init plugin v.0.1
[Save voice settings]: init plugin v.0.1
[Welcome message]: init plugin v.0.1
[Save window position]: init plugin v.0.1
[Save window size]: init plugin v.0.1
starting gespeaker
python version detected: 2.7
loading interface from /usr/share/gespeaker/data/ui/gespeaker.glade
loading controls from UI
loading languages from /usr/bin/espeak --voices
default language "german" not found in the languages list, fallback to "default"
Traceback (most recent call last):
  File "gespeaker.py", line 48, in <module>
    main = gespeakerUI.gespeakerUI()
  File "/usr/share/gespeaker/src/gespeakerUI.py", line 106, in __init__
    self.loadSettings(True)
  File "/usr/share/gespeaker/src/gespeakerUI.py", line 204, in loadSettings
    self.cboLanguages.set_active(self.defaultLanguageIndex)
TypeError: an integer is required

espeak --voices=de gives me:

Pty Language Age/Gender VoiceName File Other Languages
 5 de --/M German gmw/de
 6 de --/F german-mbrola-1 mb/mb-de1
 6 de --/M german-mbrola-2 mb/mb-de2
 6 de --/F german-mbrola-3 mb/mb-de3
 6 de --/M german-mbrola-4 mb/mb-de4
 6 de --/M german-mbrola-6 mb/mb-de6
 7 de --/F german-mbrola-5 mb/mb-de5
 7 de --/F german-mbrola-7 mb/mb-de7

Is it possible that the language selection fails because the VoiceName of German starts with a capital 'G', but gespeaker looks for "german"?
Or does language selection have nothing to do with the crash?

ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: gespeaker 0.8.6-1
ProcVersionSignature: Ubuntu 5.3.0-40.32-generic 5.3.18
Uname: Linux 5.3.0-40-generic x86_64
ApportVersion: 2.20.11-0ubuntu8.4
Architecture: amd64
CurrentDesktop: XFCE
Date: Thu Feb 20 04:56:04 2020
InstallationDate: Installed on 2017-09-03 (899 days ago)
InstallationMedia: Xubuntu 17.04 "Zesty Zapus" - Release amd64 (20170412)
PackageArchitecture: all
SourcePackage: gespeaker
UpgradeStatus: Upgraded to eoan on 2020-01-18 (32 days ago)