Preference Window does not display properly in Eclipse 2020-09

[marcel-becker]

Hi,
My Eclipse just got updated from 2020-06 to 2020-09 through the software update.
When I open the preferences window for Jeeeyul-themes settings I get 2 error dialogs. One saying an internal error has occurred. And a second one saying "The current display page contains invalid values".
I am currently on an Imac running Mac OS Catalina 10.15.6. I saw a similar problem when running Eclipse 2020-06 on an ubuntu 20.4 virtual machine running in Parallels.
If I open the preferences panel and navigate to General > Appearance > Jeeeyul's Theme, I can see the preference panel after I close the error windows. If I click on the toolbar button for Jeeeyul's preference, then I get an empty preference window after closing the error windows.
Java Version: openjdk version "14.0.2" 2020-07-14
OpenJDK Runtime Environment AdoptOpenJDK (build 14.0.2+12)
OpenJDK 64-Bit Server VM AdoptOpenJDK (build 14.0.2+12, mixed mode, sharing)

Eclipse:
Version: 2020-09 (4.17.0)
Build id: 20200910-1200