z.lua init fail: attempt to concatenate a nil value (local 'path')

[zqb-all]

z.lua init fail

mark@snode3:~/.z.lua$ lua ~/.z.lua/z.lua --init bash
ZLUA_SCRIPT="/home/mark/.z.lua/z.lua"
lua: /home/mark/.z.lua/z.lua:514: attempt to concatenate a nil value (local 'path')
stack traceback:
        /home/mark/.z.lua/z.lua:514: in function </home/mark/.z.lua/z.lua:496>
        (...tail calls...)
        /home/mark/.z.lua/z.lua:2347: in function 'z_shell_init'
        /home/mark/.z.lua/z.lua:2010: in function 'main'
        /home/mark/.z.lua/z.lua:2856: in main chunk
        [C]: in ?

mark@snode3:~/.z.lua$ lua -v
Lua 5.3.3  Copyright (C) 1994-2016 Lua.org, PUC-Rio

but it works fine on another machine, lua on that machine is also Lua 5.3.3.