TMap< FNetworkGUID, TUniquePtr< FActorDestructionInfo > > DestroyedStartupOrDormantActors
The server adds an entry into this map for every actor that is destroyed that join-in-progress clients need to know about, that is, startup actors. Also, individual UNetConnections need to keep track of FActorDestructionInfo for dormant and recently-dormant actors in addition to startup actors (because they won't have an associated channel), and this map stores those FActorDestructionInfos also.