Attempted to get trait from destroyed object (husk)

[cjshmyr]

Reported by Tesrym on IRC

    Red Alert Mod at Version release-20140608
    Operating System: Windows (Microsoft Windows NT 6.1.7600 Service Pack 1)
    Runtime Version: .NET CLR 4.0.30319.17929
    Exception of type `System.InvalidOperationException`: Attempted to get trait from destroyed object (4tnk.husk 1243 (not in world))
       at OpenRA.TraitDictionary.CheckDestroyed(Actor actor)
       at OpenRA.TraitDictionary.GetOrDefault[T](Actor actor)
       at OpenRA.Mods.RA.Buildings.BuildingInfluence.<BuildingInfluence>m__59D(Actor a)
       at System.Action`1.Invoke(T obj)
       at OpenRA.World.Remove(Actor a)
       at OpenRA.Actor.<ChangeOwner>c__AnonStoreyC2.<>m__256(World w)
       at OpenRA.World.Tick()
       at OpenRA.Game.TickInner(OrderManager orderManager)
       at OpenRA.Game.Tick(OrderManager orderManager)
       at OpenRA.Game.Run()
       at OpenRA.Program.Run(String[] args)
       at OpenRA.Program.Main(String[] args)

[Mailaender]

This problem may been revealed by #4941. I made an attempt to fix it at #5801.