title() tries to access Lua and leads to a crash

[kostja]

warning: Can't read pathname for load map: Input/output error.
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

warning: no loadable sections found in added symbol-file system-supplied DSO at 0x7fff6adfe000
Core was generated by `tarantool wal.lua: primary pri: 5118 adm: 5117          '.
Program terminated with signal 11, Segmentation fault.
#0  0x0000000000433911 in tuple_ref (tuple=0x7fa73d000aa0, count=-1) at /home/kostja/work/tarantool-2/src/box/tuple.cc:296
296     tuple->refs += count;
(gdb) bt
#0  0x0000000000433911 in tuple_ref (tuple=0x7fa73d000aa0, count=-1) at /home/kostja/work/tarantool-2/src/box/tuple.cc:296
#1  0x0000000000442899 in lbox_tuple_gc (L=0x40d3a378) at /home/kostja/work/tarantool-2/src/box/lua/tuple.cc:109
#2  0x00000000005012dc in lj_BC_FUNCC ()
#3  0x00000000004df3b0 in gc_call_finalizer ()
#4  0x00000000004df553 in gc_finalize ()
#5  0x00000000004e0011 in gc_onestep ()
#6  0x00000000004e0198 in lj_gc_step ()
#7  0x00000000004eff60 in lj_parse_keepstr ()
#8  0x00000000004ecd99 in llex ()
#9  0x00000000004ed7f6 in lj_lex_next ()
#10 0x00000000004ef519 in expr_field ()
#11 0x00000000004f17d9 in expr_primary ()
#12 0x00000000004f0492 in expr_binop ()
#13 0x00000000004f0e6d in expr ()
#14 0x00000000004f1537 in expr_list ()
#15 0x00000000004f255d in parse_chunk ()
#16 0x00000000004f2a32 in lj_parse ()
#17 0x00000000004f2c04 in cpparser ()
#18 0x000000000050161d in lj_vm_cpcall ()
#19 0x00000000004f2cbb in lua_loadx ()
#20 0x00000000004f2efc in luaL_loadbufferx ()
#21 0x00000000004f2f0d in luaL_loadbuffer ()
#22 0x00000000004f2f39 in luaL_loadstring ()
#23 0x00000000004741f7 in cfg_get (param=0x53aada "primary_port") at /home/kostja/work/tarantool-2/src/cfg.cc:39
#24 0x0000000000474235 in cfg_geti (param=0x53aada "primary_port") at /home/kostja/work/tarantool-2/src/cfg.cc:45
#25 0x000000000041c955 in title (role=0x53b843 "dumper", fmt=0x53b840 "%u") at /home/kostja/work/tarantool-2/src/tarantool.cc:111
#26 0x000000000041fc18 in box_snapshot () at /home/kostja/work/tarantool-2/src/box/box.cc:548
#27 0x00000000004420f8 in lbox_snapshot (L=0x401b8c28) at /home/kostja/work/tarantool-2/src/box/lua/call.cc:542
#28 0x00000000005012dc in lj_BC_FUNCC ()
#29 0x00000000004ebcb2 in lua_call ()
#30 0x0000000000481e4b in lbox_call (L=0x401b8c28, nargs=0, nreturns=-1) at /home/kostja/work/tarantool-2/src/lua/utils.h:213
#31 0x0000000000482bd2 in tarantool_lua_dostring (L=0x401b8c28, str=0x7fa73dc40038 "box.snapshot() ") at /home/kostja/work/tarantool-2/src/lua/init.cc:306
#32 0x0000000000482cad in tarantool_lua_do (L=0x401b8c28, out=0x7fa73dc44038, str=0x7fa73dc40038 "box.snapshot() ")
    at /home/kostja/work/tarantool-2/src/lua/init.cc:325
#33 0x0000000000482f29 in tarantool_lua (L=0x401b8c28, out=0x7fa73dc44038, str=0x7fa73dc40038 "box.snapshot() ")
    at /home/kostja/work/tarantool-2/src/lua/init.cc:377
#34 0x000000000046c3da in admin_dispatch (coio=0x7fa73dc1fef0, iobuf=0x7fa73dc20068, L=0x401b8c28) at /home/kostja/work/tarantool-2/src/admin.cc:71
#35 0x000000000046c652 in admin_handler(typedef __va_list_tag __va_list_tag *) (ap=0x7fa73dc00110) at /home/kostja/work/tarantool-2/src/admin.cc:104
#36 0x0000000000463e8f in fiber_loop (data=0x0) at /home/kostja/work/tarantool-2/src/fiber.cc:379
#37 0x00000000004b03d0 in coro_init () at /home/kostja/work/tarantool-2/third_party/coro/coro.c:95
(gdb)