bug#16769: 24.3.50; electric-pair-mode: args-out-of-range

[Xue Fuqiao]

To reproduce:

  emacs -Q --eval '(setq debug-on-error t)'
  M-x electric-pair-mode RET
  C-x h DEL

Then Emacs signals an error.  The backtrace is attached.

backtrace.txt
Description: Backtrace

In GNU Emacs 24.3.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.8.6)
 of 2014-01-25 on xfq-ThinkPad-X1-Carbon
Repository revision: 116149 larsi@gnus.org-20140125005216-vwndukqrdbq2xv4u
System Description:     Ubuntu 13.10

Configured using:
 `configure --enable-checking --disable-silent-rules
 --enable-gtk-deprecation-warnings'

Important settings:
  value of $LC_MONETARY: en_US.UTF-8
  value of $LC_NUMERIC: en_US.UTF-8
  value of $LC_TIME: en_US.UTF-8
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix