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