locale-related crash

[Dave Love]

This is a longstanding bug which I finally got round to looking at,
rather than just installing BSD mail.

I have the following locale, which is what you get for British English
on Debian; I assume other locales are similarly defined.

  LANG=en_GB.UTF-8
  LANGUAGE=en_GB:en
  LC_CTYPE="en_GB.UTF-8"
  LC_NUMERIC="en_GB.UTF-8"
  LC_TIME="en_GB.UTF-8"
  LC_COLLATE="en_GB.UTF-8"
  LC_MONETARY="en_GB.UTF-8"
  LC_MESSAGES="en_GB.UTF-8"
  LC_PAPER="en_GB.UTF-8"
  LC_NAME="en_GB.UTF-8"
  LC_ADDRESS="en_GB.UTF-8"
  LC_TELEPHONE="en_GB.UTF-8"
  LC_MEASUREMENT="en_GB.UTF-8"
  LC_IDENTIFICATION="en_GB.UTF-8"
  LC_ALL=

With that, mail(1) SEGVs if I run it to read messages:

  #0  0x00007ffff7d60ad8 in ?? () from /lib/x86_64-linux-gnu/libc.so.6
  #1  0x00007ffff7c78f2f in strdup () from /lib/x86_64-linux-gnu/libc.so.6
  #2  0x00007ffff7e82e4e in mu_strdup (s=0x0) at alloc.c:76
  #3  0x0000555555579365 in util_get_charset () at util.c:1231
  #4  0x00005555555793bb in util_rfc2047_decode (value=0x7fffffffda58) at 
util.c:1251
  #5  0x0000555555566d66 in sender_string (msg=0x555555597f90) at from.c:272
  #6  0x0000555555566ddb in hdr_from (args=0x7fffffffdac0, data=0x0) at 
from.c:290
  #7  0x000055555556678c in format_headline (seg=0x55555558d670, 
      mspec=0x555555597e20, msg=0x555555597f90) at from.c:96
  #8  0x000055555556796f in mail_from0 (mspec=0x555555597e20, 
msg=0x555555597f90, 
      data=0x0) at from.c:615
  #9  0x0000555555570002 in page_do (func=0x555555567941 <mail_from0>, data=0x0)
      at page.c:181
  #10 0x00005555555679e3 in mail_headers (argc=1, argv=0x5555555af868)
      at headers.c:34
  #11 0x000055555557716d in util_do_command (fmt=0x55555557bf02 "headers")
      at util.c:144
  #12 0x000055555556920f in main (argc=0, argv=0x7fffffffe020) at mail.c:698

This patch fixes it.

locale.diff
Description: locale.diff