Not able to set alternative editor

What steps will reproduce the problem?

1. Open TortoiseGit Settings
2. Switch to Alternative Editor
3. Switch Custom and select editor (for me it's: C:\Program Files\PSPad Editor\PSPad.exe).
4. OK
5. Reopen TortoiseGit Settings

What is the expected output? What do you see instead?

Expected: Settings of alternative editor is kept and used.

What I got: Setting of alternative editor is selected back to Notepad2 and alternative editor is never used.

What version of TortoiseGit and Git are you using? On what operating system?

TortoiseGit 2.6.0 64bit Dell Latitude with Windows 10 64bit

Please provide any additional information below.