Preferences does not open with wrong key/cert files

I selected a wrong (invalid) key file and certification in Preferences > Security, in my case a ZIP file. After restarting Gobby, the preferences dialog did not open: When selecting it from the menu, nothing happened.

Re-installing Gobby did not help.

I had to start regedit and change the private key and certificate there. After adding the correct file(s) there, I could again access the preferences dialog.