无法保存游戏，提示正在保存游戏

[CRITICAL] System update error during Serialize->SerializerSystem:

NullReferenceException: Object reference not set to an instance of an object
at Unity.Entities.EntityManager.HighestEntityIndex () [0x0005e] in <a87842490f3f4c53883b16985ce1a19e>:0
at Colossal.Serialization.Entities.EntitySerializer`1[TWriteBuffer].CreateEntityTable (Colossal.Serialization.Entities.Context context, Unity.Collections.Allocator allocator) [0x0017c] in <b147d7e6ab4d4da69ff0aeec5f834d7e>:0
at Colossal.Serialization.Entities.EntitySerializer`1[TWriteBuffer].Serialize[TWriter,TFormatTags] (Colossal.Serialization.Entities.Context context, Unity.Entities.EntityQuery query, Colossal.Serialization.Entities.BufferFormat bufferFormat, Unity.Entities.ComponentType[] requireEnabled) [0x0004d] in <b147d7e6ab4d4da69ff0aeec5f834d7e>:0
at Game.Serialization.SerializerSystem.OnUpdate () [0x000c4] in <514eb87001d34fca80a53ade169ddf06>:0
at Unity.Entities.SystemBase.Update () [0x0004e] in <a87842490f3f4c53883b16985ce1a19e>:0
at Game.UpdateSystem.Update (Game.SystemUpdatePhase phase) [0x0004e] in <514eb87001d34fca80a53ade169ddf06>:0
Colossal.Logging.CustomLogHandler:LogFormat(LogType, Object, String, Object[])
UnityEngine.Logger:LogFormat(LogType, String, Object[])
Colossal.Logging.UnityLogger:Log(Level, String, Exception)
Colossal.Logging.UnityLogger:CriticalFormat(Exception, String, Object, Object)
Game.UpdateSystem:Update(SystemUpdatePhase)
Game.Serialization.SaveGameSystem:OnUpdate()
Unity.Entities.SystemBase:Update()
Game.UpdateSystem:Update(SystemUpdatePhase)
Game.SceneFlow.GameManager:UpdateWorld()
Game.SceneFlow.GameManager:Update()