hang when restart the command after command exits

[Boyu Yang]

I use terminator on debian stable. This week I upgrade my laptop from jessie to stretch. After upgrade, terminator (version: 1.90+bzr-1705-1) can NOT restart after exit (I set exit_action = restart).

When "debugserver is True" but "debug_address is None", it will hang at function spawn_child() in file terminatorlib/terminal.py.
The line is "dbg('spawning debug session with: %s:%s' % (details[0], details[1]))".

I don't know why "debugserver is True" and "debug_address is None" on my laptop, I just run terminator as normal, but I think maybe there can add a test before use debug_address as a list.