Sometimes this mod causes a crash shortly after loading a game, or when another player joins. Trying again practically always succeeds:

1429.421 Error MainLoop.cpp:1204: Exception at tick 15302139: The mod What is missing (0.18.2) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event what-is-missing::on_tick (ID 0)
what-is-missing/async.lua:101: attempt to call field 'func' (a nil value)
stack traceback:
what-is-missing/async.lua:101: in function 'loop_next'
what-is-missing/async.lua:160: in function 'next_iteration'
what-is-missing/async.lua:202: in function 'tick'
what-is-missing/async.lua:231: in function 'on_tick'
what-is-missing/control.lua:567: in function <what-is-missing/control.lua:566>
1429.421 Error ServerMultiplayerManager.cpp:90: MultiplayerManager failed: "The mod What is missing (0.18.2) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event what-is-missing::on_tick (ID 0)
what-is-missing/async.lua:101: attempt to call field 'func' (a nil value)
stack traceback:
what-is-missing/async.lua:101: in function 'loop_next'
what-is-missing/async.lua:160: in function 'next_iteration'
what-is-missing/async.lua:202: in function 'tick'
what-is-missing/async.lua:231: in function 'on_tick'
what-is-missing/control.lua:567: in function <what-is-missing/control.lua:566>"

Hi, thank you for a good bug report. This crash is related to a change in Factorio in 0.18.28. I thought it wouldn't have any effect on my mods but I forgot something :)

I believe that I have fixed this issue now. Version 0.18.3 is now available. Please test it and see if you can break it. :)