Reproduction steps:
1. Open the attached user's project "Bolt2BugHunt.zip"
2. In the Project window under "Assets/_Project/Scenes" open "TestScene.unity"
3. Enter Play Mode

Expected result: a NullReferenceException is not thrown in the few first frames after entering Play Mode
Actual result: a NullReferenceException is thrown in the few first frames after entering Play Mode (See attached FlowFunction.mp4)

Reproduces on: Bolt 2.0.0a12 (2018.4.25f1, 2019.4.4f1, 2020.1.0b16, 2020.2.0a18)
Could not test on Bolt 1.4.12 due to no Flow Function Graph

 
{code:java}
NullReferenceException Error:
NullReferenceException: Object reference not set to an instance of an object
Unity.Bolt.BoltClassShellTrait.GetGraphInstance (Unity.Bolt.IBoltClassGraph graph) (at Assets/Bolt/Bolt.Core/Runtime/BTS/BoltClassShellTrait.cs:460)
Unity.Bolt.BoltClassGraphUnit`1[TGraph].FetchGraphInstance (Unity.Bolt.Flow flow) (at Assets/Bolt/Bolt.Flow/Runtime/Units/BTS/BoltClassGraphUnit.cs:58)
Unity.Bolt.FlowFunctionUnit.Enter (Unity.Bolt.Flow externalFlow) (at Assets/Bolt/Bolt.Flow/Runtime/Units/BTS/FlowFunctionUnit.cs:94)
Unity.Bolt.Flow.InvokeDelegate (Unity.Bolt.ControlInput input) (at Assets/Bolt/Bolt.Flow/Runtime/Flow.cs:513)
Rethrow as GraphPingException: <!GraphPing[24186,23924,54d1f27e-f914-4043-b149-49d03cb882d1,053f784b-7e95-46ab-8868-50577d3834f3]!>
Unity.Bolt.Flow.InvokeDelegate (Unity.Bolt.ControlInput input) (at Assets/Bolt/Bolt.Flow/Runtime/Flow.cs:517)
Unity.Bolt.Flow.Invoke (Unity.Bolt.ControlOutput output) (at Assets/Bolt/Bolt.Flow/Runtime/Flow.cs:408)
Unity.Bolt.EventHandlerUnit`1[TArgs].Invoke (Unity.Bolt.GraphReference reference, TArgs args) (at Assets/Bolt/Bolt.Flow/Runtime/Units/Events/EventHandlerUnit.cs:114)
Unity.Bolt.EventHandlerUnit`1+<>c_DisplayClass17_0[TArgs].<OnStartListening>b_0 (TArgs args) (at Assets/Bolt/Bolt.Flow/Runtime/Units/Events/EventHandlerUnit.cs:73)
Unity.Bolt.EventBus.Invoke[TArgs] (Unity.Bolt.EventHook hook, TArgs args) (at Assets/Bolt/Bolt.Core/Runtime/Events/EventBus.cs:158)
UnityEngine.Debug:LogException(Exception, Object)
Unity.Bolt.EventBus:Invoke(EventHook, EmptyEventArgs) (at Assets/Bolt/Bolt.Core/Runtime/Events/EventBus.cs:162)
Unity.Bolt.BoltClassShellTrait:InvokeEvent(EventHookID) (at Assets/Bolt/Bolt.Core/Runtime/BTS/BoltClassShellTrait.cs:909)
Unity.Bolt.BoltUnityClassShellTrait:Update() (at Assets/Bolt/Bolt.Core/Runtime/BTS/BoltUnityClassShellTrait.cs:33)
Unity.Bolt.BoltComponent:Update() (at Assets/Bolt/Bolt.Core/Runtime/BTS/BoltComponent.cs:128)
{code}