External editor problem (win)

Dear All,
The following settings:
...
-- External editor for editing text objects
-- must contain '%s' for the temporary filename
-- set this to nil to hide the "Editor" button on text dialogs
if os.getenv("EDITOR") then
  prefs.external_editor = os.getenv("EDITOR") .. " %s"
else
     prefs.external_editor = "c:/octave/npp/notepad++ %s"
  -- prefs.external_editor = "pluma %s"
  -- prefs.external_editor = "emacsclient %s"
  -- prefs.external_editor = nil
end

-- The name of the temporary textfile where Ipe will store text to be
-- edited with an external editor.  If set to nil, the Lua function
-- os.tmpname() will be used to create a unique name.
if config.platform == "win" then
  prefs.editable_textfile = config.latexdir .. "/temp.txt"
else
  prefs.editable_textfile = nil
end
...
worked well up to ver 7.1.9. However, ipe 7.2.* crashes
when Editor button is pressed (win 10). Did I miss something?
Thank you,
Jerzy