The mod Robot Army PvP (0.4.9) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event robotarmy_pvp::on_tick (ID 0)
LuaUnitGroup API call when LuaUnitGroup was invalid.
stack traceback:
[C]: in function 'index'
robotarmy_pvp/robolib/Squad.lua:628: in function 'validateSquadIntegrity'
robotarmy_pvp/robolib/Squad.lua:384: in function 'squadStillExists'
robotarmy_pvp/robolib/SquadControl.lua:11: in function 'updateSquad'
robotarmy_pvp/robolib/eventhandlers.lua:39: in function 'processSquadUpdatesForTick'
robotarmy_pvp/robolib/eventhandlers.lua:362: in function 'tickForces'
robotarmy_pvp/robolib/eventhandlers.lua:458: in function <robotarmy_pvp__/robolib/eventhandlers.lua:455>