C++ Failed to create an instance

Ue4 crashes when i try to create an instance (AMonster_Spawner ms), i simply try to access TArray in the gamemode Vechten class from the Monster_Spanwer class

thanks

class MYPROJECT_API AMonster_Spawner : public AActor
{
	GENERATED_BODY()
	
public:	
	// Sets default values for this actor's properties
	AMonster_Spawner();

	// Called when the game starts or when spawned
	virtual void BeginPlay() override;
	
	// Called every frame
	virtual void Tick( float DeltaSeconds ) override;
	UPROPERTY(EditAnywhere)
	TSubclassOf<AMonster_object> mesh;
	TArray<AMonster_object*> AMonster_Spawner::monster_lijst;
	int time;
	FVector loc;
	
};

class MYPROJECT_API AVechten : public AGameMode
{
	GENERATED_BODY()
	public:
		void AVechten::BeginPlay();
		void AVechten::Tick(float DeltaTime);
		AMonster_Spawner ms;
};

You checked what showing up in logs (go to Saved/Logs in project directory)?

yes:
Fatal error: [File:D:\BuildFarm\buildmachine_++UE4+Release-4.11\Engine\Source\Runtime\CoreUObject\Private\UObject\UObjectGlobals.cpp] [Line: 2239]
UObject() constructor called but it’s not the object that’s currently being constructed with NewObject. Maybe you trying to construct it on the stack which is not supported

But i just try to access an array which is in another class