I'm using Nightfall together with Will-o'-the-Wisps. It was nighttime, I accidentally killed a tree and thus released a wisp, attacked that wisp -- and crashed the game:

17318.313 Error MainLoop.cpp:1184: Exception at tick 20858483: The mod Nightfall caused a non-recoverable   error.
Please report this error to the mod author.

Error while running event Nightfall::on_tick (ID 0)
LuaUnitGroup::add_member: Attempted to add an entity of force wisp to a unit group of force enemy stack traceback:
    __Nightfall__/control.lua:107: in function 'attack'
    __Nightfall__/control.lua:67: in function <__Nightfall__/control.lua:31>
stack traceback:
    [C]: in function 'add_member'
    __Nightfall__/control.lua:107: in function 'attack'
    __Nightfall__/control.lua:67: in function <__Nightfall__/control.lua:31

If you want to, I can also send you the last autosave and the complete logfile of the crashed game.

Thanks for reporting. I think this should be an easy fix but if I run into trouble, I might followup for the extra files/info.

I think this should be an easy fix but if I run into trouble, I might followup for the extra files/info.
I really hope it's easy! After I reported this bug, the game randomly crashed on me several times with the same issue (never did this before, and I've had both mods active for quite some time), so it's getting slightly annoying … :-D

Longest part was moving all the mods/files to my new computer. New version's up that should fix it, let me know if you still have trouble.

Thanks a lot for the quick fix! I'll go and try if I can break it again. :-)