NKA: fix accessing removed hero and heroExchangeCount

AI/Nullkiller/Analyzers/HeroManager.cpp

@@ -125,6 +125,7 @@ void HeroManager::update()
 	}
 
 	std::sort(myHeroes.begin(), myHeroes.end(), scoreSort);
+	heroRoles.clear();
 
 	for(auto hero : myHeroes)
 	{

AI/Nullkiller/Pathfinding/Actors.cpp

@@ -134,6 +134,7 @@ void ChainActor::setBaseActor(HeroActor * base)
 	armyCost = base->armyCost;
 	actorAction = base->actorAction;
 	tiCache = base->tiCache;
+	actorExchangeCount = base->actorExchangeCount;
 }
 
 void HeroActor::setupSpecialActors()