This is likely related to WT-1473.  The log-append job failed with:
(gdb) bt
#0  __strlen_sse42 () at ../sysdeps/x86_64/multiarch/strlen-sse4.S:32
WT-1  0x000000000044ca44 in __wt_filename (session=0x7ffb00439780, name=0x0, path=0x7ffaff3fcd60) at ../src/support/filename.c:18
WT-2  0x0000000000426dae in __wt_dirlist (session=0x7ffb00439780, dir=0x0, prefix=0x4c1a36 "WiredTigerLog", flags=2, dirlist=0x7ffaff3fcdb0, countp=0x7ffaff3fcdd0)
    at ../src/os_posix/os_dir.c:32
WT-3  0x000000000047b80e in __log_archive_once (session=0x7ffb00439780, backup_file=0) at ../src/conn/conn_log.c:140
WT-4  0x000000000047bae2 in __log_server (arg=0x7ffb00439780) at ../src/conn/conn_log.c:305
WT-5  0x00007ffb012d5ddb in start_thread (arg=0x7ffaff3fd700) at pthread_create.c:301
WT-6  0x00007ffb01023a1d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:115
(gdb) p conn->log_path
$2 = 0x0
However, running it again and it goes away. This needs more investigation.
- related to
- 
                    WT-1 placeholder WT-1 - Closed
 
- 
                    WT-2 What does metadata look like? - Closed
 
- 
                    WT-3 What file formats are required? - Closed
 
- 
                    WT-4 Flexible cursor traversals - Closed
 
- 
                    WT-5 How does pget work: is it necessary? - Closed
 
- 
                    WT-6 Complex schema example - Closed
 
- 
                    WT-1473 Allow printlog to work without recovery. - Closed
 
- 
                    WT-1480 format: core dump with NULL log_path - Closed