Fatal error: assertion failed, file insdel.c, line 1124, VALID_BYTIND_P (buf, x)

Fatal error (6).
Your files have been auto-saved.
Use `M-x recover-session' to recover them.

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version of XEmacs, please check to see if your crash is described
there, as there may be a workaround available.
Otherwise, please report this bug by running the send-pr
script included with XEmacs, or selecting `Send Bug Report'
from the help menu.
As a last resort send ordinary email to `crashes@xemacs.org'.
*MAKE SURE* to include the information in the command
M-x describe-installation.

If at all possible, *please* try to obtain a C stack backtrace;
it will help us immensely in determining what went wrong.
To do this, locate the core file that was produced as a result
of this crash (it's usually called `core' and is located in the
directory in which you started the editor, or maybe in your home
directory), and type

  gdb /usr/local/bin/xemacs core

then type `where' when the debugger prompt comes up.
(If you don't have GDB on your system, you might have DBX,
or XDB, or SDB.  A similar procedure should work for all of
these.  Ask your system administrator if you need more help.)

Lisp backtrace follows:

  # (unwind-protect ...)
  # (unwind-protect ...)
  # (unwind-protect ...)
  # bind (tempbuf coding-system str)
  decode-coding-string("己所不欲，勿施於人。" cn-gb-2312)
  # bind (s)
  (let ((s "~{<:Ky2;S{#,NpJ)l6HK!#~}")) (put-text-property 0 (length s) (quote face) (quote bold) s) (setq s (test-decode s)) (decode-coding-string s (quote cn-gb-2312)))
)
  eval((let ((s "~{<:Ky2;S{#,NpJ)l6HK!#~}")) (put-text-property 0 (length s) (quote face) (quote bold) s) (setq s (test-decode s)) (decode-coding-string s (quote cn-gb-2312))))
  # bind (expr)
  eval-interactive((let ((s "~{<:Ky2;S{#,NpJ)l6HK!#~}")) (put-text-property 0 (length s) (quote face) (quote bold) s) (setq s (test-decode s)) (decode-coding-string s (quote cn-gb-2312))))
  # bind (standard-output opoint ignore-quotes eval-last-sexp-arg-internal)
  eval-last-sexp(nil)
  # bind (command-debug-status)
  call-interactively(eval-last-sexp)
  # (condition-case ... . error)
  # (catch top-level ...)