Crash on quit after calling blueprint event with actor parameter

When I call a blueprint event in 4.0.2, with an actor parameter as follows:

UCLASS(Blueprintable, BlueprintType)
class USneakPeakPlayerActionType : public UObject{
public:
	GENERATED_UCLASS_BODY()

	UPROPERTY(EditAnywhere, Category="Player Action")
	FText Name;

	UPROPERTY(EditAnywhere, Category = "Player Action")
	float Cooldown;

	UPROPERTY(EditAnywhere, Category="Player Action")
	uint32 bEnabled : 1;

public:
	UFUNCTION(BlueprintImplementableEvent, Category = "Player Action")
	virtual void OnUse( class ASneakPeakGL4Character* Character);
};

the editor crashes when exiting the game. It gives the following error message in the output log:

[2014.05.20-12.09.48:506][923]LogReferenceChain: Searching referencers for Game. This may take several minutes.
[2014.05.20-12.09.48:571][923]LogReferenceChain: Generating reference graph ...
[2014.05.20-12.09.48:574][923]LogReferenceChain: Level 0 has 7 nodes ...
[2014.05.20-12.09.48:578][923]LogReferenceChain: Level 1 added 92 nodes ...
[2014.05.20-12.09.48:583][923]LogReferenceChain: Level 2 added 372 nodes ...
[2014.05.20-12.09.48:587][923]LogReferenceChain: Level 3 added 592 nodes ...
[2014.05.20-12.09.48:591][923]LogReferenceChain: Level 4 added 30 nodes ...
[2014.05.20-12.09.48:596][923]LogReferenceChain: Level 5 added 16 nodes ...
[2014.05.20-12.09.48:602][923]LogReferenceChain: Level 6 added 23 nodes ...
[2014.05.20-12.09.48:606][923]LogReferenceChain: Level 7 added 9 nodes ...
[2014.05.20-12.09.48:610][923]LogReferenceChain: Level 8 added 6 nodes ...
[2014.05.20-12.09.48:615][923]LogReferenceChain: Level 9 added 11 nodes ...
[2014.05.20-12.09.48:619][923]LogReferenceChain: Level 10 added 12 nodes ...
[2014.05.20-12.09.48:625][923]LogReferenceChain: Level 11 added 0 nodes ...
[2014.05.20-12.09.48:625][923]LogReferenceChain: Generating reference chains ...
[2014.05.20-12.09.48:625][923]LogReferenceChain:   
[2014.05.20-12.09.48:626][923]LogReferenceChain: External Referencers:
[2014.05.20-12.09.48:626][923]LogReferenceChain:   
[2014.05.20-12.09.48:626][923]LogReferenceChain: (root) (standalone) Blueprint /Game/Actions/LargeSnowballAction.LargeSnowballAction->GeneratedClass
[2014.05.20-12.09.49:060][923]LogReferenceChain:   BlueprintGeneratedClass /Game/Actions/LargeSnowballAction.LargeSnowballAction_C->
[2014.05.20-12.09.49:061][923]LogReferenceChain:     LargeSnowballAction_C /Game/Actions/LargeSnowballAction.Default__LargeSnowballAction_C->K2Node_Event_Character
[2014.05.20-12.09.49:061][923]LogReferenceChain:       MyCharacter_C /Game/Maps/UEDPIE_0_Game.Game:PersistentLevel.MyCharacter_C_0->Property
[2014.05.20-12.09.49:062][923]LogReferenceChain:         Level /Game/Maps/UEDPIE_0_Game.Game:PersistentLevel->OwningWorld
[2014.05.20-12.09.49:062][923]LogReferenceChain:           (target) World /Game/Maps/UEDPIE_0_Game.Game
[2014.05.20-12.09.49:062][923]LogReferenceChain:   
[2014.05.20-12.09.49:062][923]LogReferenceChain: (root) SneakPeakGL4GameMode /Script/SneakPeakGL4.Default__SneakPeakGL4GameMode->DefaultPawnClass
[2014.05.20-12.09.49:063][923]LogReferenceChain:   BlueprintGeneratedClass /Game/Blueprints/MyCharacter.MyCharacter_C->
[2014.05.20-12.09.49:063][923]LogReferenceChain:     MyCharacter_C /Game/Blueprints/MyCharacter.Default__MyCharacter_C->AvailableActions
[2014.05.20-12.09.49:063][923]LogReferenceChain:       BlueprintGeneratedClass /Game/Actions/LargeSnowballAction.LargeSnowballAction_C->
[2014.05.20-12.09.49:063][923]LogReferenceChain:         LargeSnowballAction_C /Game/Actions/LargeSnowballAction.Default__LargeSnowballAction_C->K2Node_Event_Character
[2014.05.20-12.09.49:064][923]LogReferenceChain:           MyCharacter_C /Game/Maps/UEDPIE_0_Game.Game:PersistentLevel.MyCharacter_C_0->Property
[2014.05.20-12.09.49:064][923]LogReferenceChain:             Level /Game/Maps/UEDPIE_0_Game.Game:PersistentLevel->OwningWorld
[2014.05.20-12.09.49:064][923]LogReferenceChain:               (target) World /Game/Maps/UEDPIE_0_Game.Game
[2014.05.20-12.09.49:065][923]LogReferenceChain:   
[2014.05.20-12.09.49:065][923]LogReferenceChain: (root) (standalone) Blueprint /Game/Blueprints/MyCharacter.MyCharacter->GeneratedClass
[2014.05.20-12.09.49:065][923]LogReferenceChain:   BlueprintGeneratedClass /Game/Blueprints/MyCharacter.MyCharacter_C->
[2014.05.20-12.09.49:065][923]LogReferenceChain:     MyCharacter_C /Game/Blueprints/MyCharacter.Default__MyCharacter_C->AvailableActions
[2014.05.20-12.09.49:066][923]LogReferenceChain:       BlueprintGeneratedClass /Game/Actions/LargeSnowballAction.LargeSnowballAction_C->
[2014.05.20-12.09.49:066][923]LogReferenceChain:         LargeSnowballAction_C /Game/Actions/LargeSnowballAction.Default__LargeSnowballAction_C->K2Node_Event_Character
[2014.05.20-12.09.49:066][923]LogReferenceChain:           MyCharacter_C /Game/Maps/UEDPIE_0_Game.Game:PersistentLevel.MyCharacter_C_0->Property
[2014.05.20-12.09.49:066][923]LogReferenceChain:             Level /Game/Maps/UEDPIE_0_Game.Game:PersistentLevel->OwningWorld
[2014.05.20-12.09.49:067][923]LogReferenceChain:               (target) World /Game/Maps/UEDPIE_0_Game.Game
[2014.05.20-12.09.49:067][923]LogReferenceChain:   
[2014.05.20-12.09.49:067][923]LogReferenceChain: (root) (standalone) Blueprint /Game/Blueprints/MyCharacter.MyCharacter->SimpleConstructionScript
[2014.05.20-12.09.49:067][923]LogReferenceChain:   SimpleConstructionScript /Game/Blueprints/MyCharacter.MyCharacter_C:SimpleConstructionScript_0->Property
[2014.05.20-12.09.49:068][923]LogReferenceChain:     BlueprintGeneratedClass /Game/Blueprints/MyCharacter.MyCharacter_C->
[2014.05.20-12.09.49:068][923]LogReferenceChain:       MyCharacter_C /Game/Blueprints/MyCharacter.Default__MyCharacter_C->AvailableActions
[2014.05.20-12.09.49:068][923]LogReferenceChain:         BlueprintGeneratedClass /Game/Actions/LargeSnowballAction.LargeSnowballAction_C->
[2014.05.20-12.09.49:068][923]LogReferenceChain:           LargeSnowballAction_C /Game/Actions/LargeSnowballAction.Default__LargeSnowballAction_C->K2Node_Event_Character
[2014.05.20-12.09.49:069][923]LogReferenceChain:             MyCharacter_C /Game/Maps/UEDPIE_0_Game.Game:PersistentLevel.MyCharacter_C_0->Property
[2014.05.20-12.09.49:069][923]LogReferenceChain:               Level /Game/Maps/UEDPIE_0_Game.Game:PersistentLevel->OwningWorld
[2014.05.20-12.09.49:069][923]LogReferenceChain:                 (target) World /Game/Maps/UEDPIE_0_Game.Game
[2014.05.20-12.09.49:069][923]LogReferenceChain:   
[2014.05.20-12.09.49:070][923]LogReferenceChain: (root) (standalone) Blueprint /Game/Blueprints/MyCharacter.MyCharacter->SkeletonGeneratedClass
[2014.05.20-12.09.49:070][923]LogReferenceChain:   BlueprintGeneratedClass /Game/Blueprints/MyCharacter.SKEL_MyCharacter_C->SimpleConstructionScript
[2014.05.20-12.09.49:070][923]LogReferenceChain:     SimpleConstructionScript /Game/Blueprints/MyCharacter.MyCharacter_C:SimpleConstructionScript_0->Property
[2014.05.20-12.09.49:070][923]LogReferenceChain:       BlueprintGeneratedClass /Game/Blueprints/MyCharacter.MyCharacter_C->
[2014.05.20-12.09.49:071][923]LogReferenceChain:         MyCharacter_C /Game/Blueprints/MyCharacter.Default__MyCharacter_C->AvailableActions
[2014.05.20-12.09.49:071][923]LogReferenceChain:           BlueprintGeneratedClass /Game/Actions/LargeSnowballAction.LargeSnowballAction_C->
[2014.05.20-12.09.49:071][923]LogReferenceChain:             LargeSnowballAction_C /Game/Actions/LargeSnowballAction.Default__LargeSnowballAction_C->K2Node_Event_Character
[2014.05.20-12.09.49:071][923]LogReferenceChain:               MyCharacter_C /Game/Maps/UEDPIE_0_Game.Game:PersistentLevel.MyCharacter_C_0->Property
[2014.05.20-12.09.49:072][923]LogReferenceChain:                 Level /Game/Maps/UEDPIE_0_Game.Game:PersistentLevel->OwningWorld
[2014.05.20-12.09.49:072][923]LogReferenceChain:                   (target) World /Game/Maps/UEDPIE_0_Game.Game
D:\BuildFarm\buildmachine_++depot+UE4-Releases+4.0\Engine\Source\Developer\MessageLog\Private\Model\MessageLogListingModel.cpp(70): Fatal error:
Critical Error Package /Game/Maps/UEDPIE_0_Game Object from PIE level still referenced. Shortest path from root:    (Object is not currently rooted)

As soon as I either remove the actor parameter, don’t call the event, or don’t have the event implemented in blueprint the crash does not occur.