The title says it all; I'm on 0.18.22, though the error seems like it's probably Warptorio that's updated something. Probably some functionality moved into Planetorio if I had to guess without actually diving through any of the scripts.
The error in full:
The mod Warptorio2 Cold Planets (0.18.4) caused a non-recoverable error.
Please report this error to the mod author.
Error while running event warptorio_cold_planets::on_init()
No such function: warptorio.registerplanet
stack traceback:
warptorio_cold_planets/control.lua:280: in function 'RegisterPlanets'
warptorio_cold_planets/control.lua:9: in function <warptorio_cold_planets/control.lua:7>
stack traceback:
[C]: in function 'call'
warptorio_cold_planets/control.lua:280: in function 'RegisterPlanets'
warptorio_cold_planets/control.lua:9: in function <warptorio_cold_planets/control.lua:7>