Empty sub-string expansion bug

[David Purdy]

Configuration Information [Automatically generated, do not change]:
Machine: i486
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='i486'
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='i486-pc-linux-gnu'
-DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL
-DHAVE_CONFIG_H   -I.  -I../bash -I../bash/include -I../bash/lib   -g -O2
uname output: Linux lnxdavid 2.6.17-2-686 #1 SMP Wed Sep 13 16:34:10 UTC 2006
i686 GNU/Linux
Machine Type: i486-pc-linux-gnu

Bash Version: 3.1
Patch Level: 17
Release Status: release

Description:
        Substring operations that are meant to return an empty string ""
sometimes return character "\177" instead.

Repeat-By:
        A=""
        B="${A:0}"
        touch "/tmp/test/TEST${A:0}"

        -> touch: cannot touch `/tmp/test/TEST\177': No such file or directory

        touch "/tmp/test/TEST$B"

        -> touch: cannot touch `/tmp/test/TEST': No such file or directory

        The example above is contrived, here is another (more realistic) 
example:

        A="abc"
        touch "/tmp/test/TEST${A:3}"

        -> touch: cannot touch `/tmp/test/TEST\177': No such file or directory


Fix:
        Bash script work-around: Use an intermediate variable until the bug is
fixed.