New REPL crashes on an empty DELETE_WORD_BACKWARDS (^W) followed by CLEAR_TO_START (^K)

Bug report

Bug description:

If, in the REPL, you:

1. Delete the current word, backward, on an empty line using Control-W, then
2. Delete to the end of line, using Control-K

The REPL will crash with an exception in readline.

Note: ^ denotes pressing the Control or Command key when pressing the next character.

>>> ^W^KTraceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "/usr/lib64/python3.13/_pyrepl/__main__.py", line 6, in <module>
    __pyrepl_interactive_console()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/usr/lib64/python3.13/_pyrepl/main.py", line 59, in interactive_console
    run_multiline_interactive_console(console)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^
  File "/usr/lib64/python3.13/_pyrepl/simple_interact.py", line 143, in run_multiline_interactive_console
    statement = multiline_input(more_lines, ps1, ps2)
  File "/usr/lib64/python3.13/_pyrepl/readline.py", line 389, in multiline_input
    return reader.readline()
           ~~~~~~~~~~~~~~~^^
  File "/usr/lib64/python3.13/_pyrepl/reader.py", line 802, in readline
    self.handle1()
    ~~~~~~~~~~~~^^
  File "/usr/lib64/python3.13/_pyrepl/reader.py", line 785, in handle1
    self.do_cmd(cmd)
    ~~~~~~~~~~~^^^^^
  File "/usr/lib64/python3.13/_pyrepl/reader.py", line 710, in do_cmd
    command.do()
    ~~~~~~~~~~^^
  File "/usr/lib64/python3.13/_pyrepl/commands.py", line 157, in do
    self.kill_range(r.pos, eol + 1)
    ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.13/_pyrepl/commands.py", line 71, in kill_range
    r.kill_ring[-1] = r.kill_ring[-1] + text
                      ~~~~~~~~~~~^^^^

This exception is caused since kill_range is not called on an empty backward_kill_word, causing kill_ring to be empty: https://github.com/pypy/pyrepl/blob/ca192a80b76700118b9bfd261a3d098b92ccfc31/pyrepl/commands.py#L152-L156

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-131452

Inizia in pyrepl/commands.py intorno alle righe 152-156, dove sono descritti l’eliminazione all’indietro delle parole e kill_range. Riproduci nel REPL la sequenza ^W seguita da ^K su una riga vuota e traccia lo stato del kill-ring. Il lavoro è completato quando la sequenza non solleva più l’eccezione readline segnalata; il PR collegato gh-131452 indica che il lavoro è già in corso.