Segfault when panel.replace() is given a detached window #155860

Bug description:

curses.screen.close() detaches the screen's standard window. panel.replace() accepts that detached window and stores its NULL window in the panel, and the panel then dereferences it inside libpanel.

import curses, curses.panel, pty

screen = curses.newterm(None, pty.openpty()[1], pty.openpty()[1])
win = screen.stdscr
panel = curses.panel.new_panel(curses.newwin(3, 6, 0, 0))
screen.close()                  # win is now detached
panel.replace(win)              # accepted, stores a NULL window
panel.move(1, 1)                # dereferenced inside libpanel

$ TERM=xterm-256color ./python repro.py; echo "rc=$?"
Segmentation fault (core dumped)
rc=139

Expected: panel.replace() raises curses.panel.error, the way new_panel() already does when handed the same window.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-155860: Reject a detached window in panel.replace() #155861