sgt-puzzles: Galaxies won't load from launcher (20.04)

[Chris Guiver]

Loading SGT Puzzles Collection from menu the launcher appears
On selecting Galaxies from the selection of games

Expected outcome:
-----------------

I expect the game to start

Actual outcome:
---------------

I get a flash, a brief-flash of a window appears then it returns to the SGT Puzzles Collection window which shows Galaxies in the middle and Please wait... and spinning..

It remains there

If opened from terminal I get the following

guiverc@d960-ubu2:/de2900/ubuntu_podcasts/ubu_sec$ sgt-launcher
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/sgtlauncher/SgtSocketLauncher.py", line 52, in callback
    withdrawn = self.wait_for_window_withdraw()
  File "/usr/lib/python3/dist-packages/sgtlauncher/SgtSocketLauncher.py", line 89, in wait_for_window_withdraw
    withdrawn = is_withdrawn(self.window_id)
  File "/usr/lib/python3/dist-packages/sgtlauncher/SgtSocketLauncher.py", line 178, in is_withdrawn
    withdrawn = not property_reply or property_value[0] == 0
TypeError: 'NoneType' object is not subscriptable

The python3 messages appear when selecting "Galaxies", but operation is the same as described.

Running sgt-galaxies from terminal is as expected.

FYI: My current desktop is LXQt/Lubuntu, but `xubuntu-desktop` is installed