TypeError: QueryValueEx() argument 2 must be str or None, not bytes

From the settings screen, TortoiseHG tab, I clicked the dropdown button for "CLI Editor" and instantly the following error was shown:

    #!python
    ** Mercurial version (6.1.2+hg305.a13398ef7e55).  TortoiseHg version (6.1.2+12-e8682f4e7a70)
    ** Command: 
    ** CWD: C:\Windows\system32
    ** Encoding: cp1252
    ** Extensions loaded: absorb, amend, convert, eol, evolve 10.5.1, extdiff, graphlog, hggit 1.0.0 (dulwich 0.20.35), histedit, rebase, relink, share, strip, topic 0.24.1.dev, tortoisehg.util.configitems, transplant
    ** Python version: 3.9.12 (tags/v3.9.12:b28265d, Mar 23 2022, 23:52:46) [MSC v.1929 64 bit (AMD64)]
    ** Windows version: sys.getwindowsversion(major=6, minor=2, build=9200, platform=2, service_pack='')
    ** Processor architecture: x64
    ** Qt-5.15.2 PyQt-5.15.6 QScintilla-2.13.2
    Traceback (most recent call last):
      File "tortoisehg\hgqt\settings.pyc", line 165, in showPopup
      File "tortoisehg\hgqt\settings.pyc", line 603, in findEditors
      File "tortoisehg\util\editor.pyc", line 141, in findeditors
      File "tortoisehg\util\editor.pyc", line 141, in <listcomp>
      File "tortoisehg\util\editor.pyc", line 50, in _findtool
      File "mercurial\windows.pyc", line 691, in lookupreg
    TypeError: QueryValueEx() argument 2 must be str or None, not bytes

The existing value in that dropdown is:

If I tab into the text portion of the control instead, I can type in it and save settings OK.

I'm using version:

version 6.1.2+12-e8682f4e7a70
with Mercurial-6.1.2+hg305.a13398ef7e55, Python-3.9.12, PyQt-5.15.6, Qt-5.15.2