"[ -n ${emptyvariable} ]" returns success

[jik]

Configuration Information [Automatically generated, do not change]:
Machine: i386
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='i386' 
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='i386-redhat-linux-gnu' 
-DCONF_VENDOR='redhat' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL 
-DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib  -D_GNU_SOURCE 
-D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -O2 -g -pipe -Wall 
-Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector 
--param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic 
-fasynchronous-unwind-tables
uname output: Linux jik2.kamens.brookline.ma.us 2.6.22.5-71.fc7 #1 SMP Fri Aug 
24 23:50:35 EDT 2007 i686 i686 i386 GNU/Linux
Machine Type: i386-redhat-linux-gnu

Bash Version: 3.2
Patch Level: 25
Release Status: release

Description:
        foo=
        [ -n ${foo} ] && echo true

        Prints "true".

        Should probably print an error, since after the command is
        expanded there are only three arguments, so the final ] should
        be interpreted as the argument to -n, thus leaving the command
        with a missing ] terminator.

        Alternatively, if you want to be forgiving and allow the shell
        to realize that there was an empty variable before the ], then
        the command should return false, since the variable is empty.

Repeat-By:
        See above.