another one:

NullReferenceException: Object reference not set to an instance of an object
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QuestManager.GiveQuestArmyKillReward (.Empire killerEmpire, .Encounter encounter)
QuestManager.CheckForArmyKill (.EventEncounterStateChange encounterEvent)
QuestManager.EventService_EventRaise (System.Object sender, Amplitude.Unity.Event.EventRaiseEventArgs e)
Amplitude.Unity.Event.EventManager.Notify (Amplitude.Unity.Event.Event notification)
Encounter.OnEncounterStateChange (.EncounterStateChangeEventArgs e)
Encounter.set_EncounterState (EncounterState value)
GameClient+<EndEncounterProcessor>c__Iterator5E4.MoveNext ()
Amplitude.Coroutine.Run ()
GameClient.ProcessOrders ()
GameInterface.UpdateMessageBoxAndProcessOrders ()
GameClient.UpdateMessageBoxAndProcessOrders ()
Session.Update ()
Amplitude.Unity.Session.SessionManager.LateUpdate ()

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V1.5.7 S3  (64-bit)

Easily reproducible.   Load this game and press "next turn". 

Mezari - Hard.zip

Any dev care to comment if this bug might be messing up my quests?   "Give Quest Army Kill Reward" looks suspiciously like the early Mezari faction quest.   :\

There seem to be a couple rough edges with 1.5.7,  has anyone seen any dev comment on further patches?   I don't follow the forums religiously.

Thanks!