persistent-nodemap: avoid writing nodemap for empty revlog The format cannot encode the lack of tip_rev. There is currently nothing known to write such empty nodemap right now, but the change we are preparing on default reveal this issue. So I had rather fix it on stable.

histedit: remove superfluous echo() and endwin() calls (issue6859) ncurses patchlevel 20231111 started returning an error from endwin() if called twice without a intervening screen update. Per Sven Joachim in https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1058041#17: "AFAICS, invoking curses.echo() and curses.endwin() is superfluous because curses.wrapper already does that for you, and calling curses.endwin() twice throws an error with the newer ncurses. Removing those two lines should fix the problem."