check_locale() and the empty string

The following SQL succeeds:

  create database foodb with
    template = template0
    encoding = 'UTF8'
    lc_collate=''
    lc_ctype='';

(any other template fails because it actually checks for a match against
the template).

The problem seems to be in check_locale(), which just checks for a
non-NULL return value from setlocale(). However, the manual for
setlocale() says:

  If locale is "", each part of the locale that should be modified
  is set according  to  the  environment  variables.   The details
  are implementation-dependent.

Surely we don't want it to be set from the environment, right?

Regards,
    Jeff Davis