Bug#988086: Exim delivery process crashes on each mail with NULL-pointer

[halfdog]

Package: exim4-daemon-light
Version: 4.94-19
Severity: grave

Yesterdays 21nails update causes Exim to fail delivery of any
messages. This might be related to using syslogging only without
any file logging configured:

Core was generated by `/usr/sbin/exim4 -Mc 1ldzSC-0001yw-RY'.
Program terminated with signal SIGSEGV, Segmentation fault.
(gdb) bt
#0  0x00005594e218a364 in log_create (name=0x7ffe89730380 "") at log.c:283
#1  0x00005594e218a4a6 in log_create_as_exim (
    name=name at entry=0x7ffe89730380 "") at log.c:336
#2  0x00005594e218aa20 in open_log (fd=fd at entry=0x5594e2256ed0 <mainlogfd>, 
    type=type at entry=0, tag=tag at entry=0x0) at log.c:489
#3  0x00005594e218b17b in open_logs () at log.c:1451
#4  0x00005594e21e1ed8 in appendfile_transport_setup (tblock=0x5594e2430688, 
    addrlist=<optimized out>, dummy=<optimized out>, uid=<optimized out>, 
    gid=<optimized out>, errmsg=0x5594e243a200) at appendfile.c:238
#5  0x00005594e21596ad in deliver_local (addr=addr at entry=0x5594e243a130, 
    shadowing=shadowing at entry=0) at deliver.c:2322
#6  0x00005594e21645f9 in do_local_deliveries () at deliver.c:3015
#7  deliver_message (id=<optimized out>, forced=forced at entry=0, 
    give_up=give_up at entry=0) at deliver.c:7209
#8  0x00005594e21456a3 in main (argc=3, cargv=<optimized out>) at exim.c:4644


   0x00005594e218a355 <+101>:   call   0x5594e2140bc0 <strrchr at plt>
   0x00005594e218a35a <+106>:   xor    %ecx,%ecx
   0x00005594e218a35c <+108>:   mov    $0x1e8,%edx
   0x00005594e218a361 <+113>:   mov    %rbp,%rsi
=> 0x00005594e218a364 <+116>:   movb   $0x0,(%rax)
   0x00005594e218a367 <+119>:   xor    %edi,%edi
   0x00005594e218a369 <+121>:   mov    %rax,%r13
   0x00005594e218a36c <+124>:   call   0x5594e21667e0 <directory_make>

rax            0x0                 0