builtin "fc -s" with a null string can cause bash to crash

[Jeremy S Bygott]

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-pc-linux-gnu' 
-DCONF_VENDOR='pc' -DSHELL -DHAVE_CONFIG_H  -D_FILE_OFFSET_BITS=64  -I.  
-I/home/swt/doko/export/packages/bash/bash-2.03 
-I/home/swt/doko/export/packages/bash/bash-2.03/lib -I/usr/include -g -O2
uname output: Linux debian 2.2.17 #1 Sun Jun 25 09:24:41 EST 2000 i686 unknown
Machine Type: i386-pc-linux-gnu

Bash Version: 2.03
Patch Level: 0
Release Status: release

Description:

        The bash builtin command "fc -s PAT=REP" should repeat the
        most recent command with PAT replaced by REP.  For example,

                debian:~$ echo Hello world!
                Hello world!
                debian:~$ fc -s ello=i
                echo Hi world!
                Hi world!

        It is sometimes okay to use the null string for REP, for
        example:

                debian:~$ echo Hello world!
                Hello world!
                debian:~$ fc -s ell=''
                echo Ho world!
                Ho world!
                debian:~$

        However, if PAT matches the beginning of the most recent
        command and REP is the null string, the shell hangs.

        I'm not a shell wizard and this is my first bug report, so I
        hope it really is a bug.

Repeat-By:

                debian:~$ zzzecho Hello world!
                bash: zzzecho: command not found
                debian:~$ fc -s zzz=''

        The shell should echo the command 'echo Hello world!' and then
        execute it.  Instead, the shell hangs.