systemctl: do not segfault when we cannot find template unit (#4915)

Core was generated by `systemctl cat test@.target test@.service'.
Program terminated with signal SIGSEGV, Segmentation fault.
32              movdqu  (%rdi), %xmm0
(gdb) bt
-0  strrchr () at ../sysdeps/x86_64/strrchr.S:32
-1  0x00007f57fdf837fe in __GI___basename (filename=0x0) at basename.c:24
-2  0x000055b8a77d0d91 in unit_find_paths (bus=0x55b8a9242f90, unit_name=0x55b8a92428f0 "test@.service", lp=0x7ffdc9070400, fragment_path=0x7ffdc90703e0, dropin_paths=0x7ffdc90703e8) at src/systemctl/systemctl.c:2584
-3  0x000055b8a77dbae5 in cat (argc=3, argv=0x7ffdc9070678, userdata=0x0) at src/systemctl/systemctl.c:5324
-4  0x00007f57fe55fc6b in dispatch_verb (argc=5, argv=0x7ffdc9070668, verbs=0x55b8a77f1c60 <verbs>, userdata=0x0) at src/basic/verbs.c:92
-5  0x000055b8a77e477f in systemctl_main (argc=5, argv=0x7ffdc9070668) at src/systemctl/systemctl.c:8141
-6  0x000055b8a77e5572 in main (argc=5, argv=0x7ffdc9070668) at src/systemctl/systemctl.c:8412

The right behaviour is not easy in this case. Implement some "sensible" logic.

Fixes #4912.

0 files changed, 0 insertions, 0 deletions