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

從 pyrepl/commands.py 的第 152-156 行附近開始，這裡描述了向後刪除單字和 kill_range。在 REPL 中重現空白行上的 ^W 後接 ^K 序列，並追蹤 kill-ring 的狀態。當該序列不再引發回報的 readline 例外時即表示完成；連結的 PR gh-131452 顯示相關工作已經在進行中。