[BUG] applying zero offset to null pointer growjobtab() src/jobs.c:819:34

Hello Dash maintainers,

I encountered a bug in Dash in commit b4ef25d7 and would like to report
it. The details are provided below.


jobs.c:819:34: runtime error: applying zero offset to null pointer
     #0 0x5adb67991deb in growjobtab /upstream/ubsan/dash/src/jobs.c:819:34
     #1 0x5adb67991985 in makejob /upstream/ubsan/dash/src/jobs.c:774:9
     #2 0x5adb679937a8 in vforkexec /upstream/ubsan/dash/src/jobs.c:992:7
     #3 0x5adb6796edcc in evalcommand /upstream/ubsan/dash/src/eval.c:916:9
     #4 0x5adb6796c0ac in evaltree /upstream/ubsan/dash/src/eval.c:305:12
     #5 0x5adb6799818c in cmdloop /upstream/ubsan/dash/src/main.c:246:8
     #6 0x5adb67997e4b in main /upstream/ubsan/dash/src/main.c:180:3
     #7 0x7a95463ad249 in __libc_start_call_main 
csu/../sysdeps/nptl/libc_start_call_main.h:58:16
     #8 0x7a95463ad304 in __libc_start_main csu/../csu/libc-start.c:360:3
     #9 0x5adb6793a930 in _start (/upstream/ubsan/dash/src/dash+0x42930) 
(BuildId: bf877a87a1c989c4907f14ce16668321dedc5edd)

SUMMARY: UndefinedBehaviorSanitizer: nullptr-with-offset jobs.c:819:34

Environment:

Debian-12, x86-64
clang-19 compiler

Steps to reproduce:

./autogen.sh
CC=clang CFLAGS=" -fsanitize=undefined -g " ./configure 
--disable-fnmatch --disable-lineno --disable-glob
make
cd src
echo "sudo" | ./dash

You can put any installed utility instead of sudo on your system, except 
builtin commands.