RandomElementByWeight with totalWeight=0 - use TryRandomElementByWeight.
Verse.Log:Error(String)
Verse.GenCollection:RandomElementByWeight(IEnumerable`1, Func`2)
RumoursAndDeception.InteractionWorker_SpreadRumours:ChooseGossipTarget(Pawn, Pawn)
RumoursAndDeception.InteractionWorker_SpreadRumours:Interacted(Pawn, Pawn, List`1)
RimWorld.Pawn_InteractionsTracker:TryInteractWith(Pawn, InteractionDef)
Hospitality.Harmony.TryInteractRandomly:Replacement(Pawn_InteractionsTracker, Boolean&)
RimWorld.Pawn_InteractionsTracker:TryInteractRandomly_Patch1(Object)
RimWorld.Pawn_InteractionsTracker:InteractionsTrackerTick()
Verse.Pawn:Tick()
Verse.TickList:Tick()
Verse.TickManager:DoSingleTick()
Verse.TickManager:TickManagerUpdate()
Verse.Game:UpdatePlay()
Verse.Root_Play:Update()

Not sure what happened, just suddenly jumped out the red warning. Looks like it has something to do with the Hospitallity mod...