GAS: Crash when adding cooldown effect

[CoolRabi]

I am using the GAS. I have a spell, which works, unless I add a cooldown effect. Then, the game immediately crashes when I try to activate this spell/ability. I pinpointed this to an invalid pointer inside of the member ActiveGameplayEffects of the responsible AbilitySystemComponent (ASC).
Somehow, this ASC is not created correctly I believe. This all happens in an item class (RTSItem) I created (+ inventory component).

Here is how I create the ASC:

ARTSItem::ARTSItem()
	:AssociatedAbility(nullptr), Icon(nullptr)
{
 	// Set this actor to call Tick() every frame.  You can turn this off to improve performance if you don't need it.
	PrimaryActorTick.bCanEverTick = true;
	bAlwaysRelevant = true;
	this->SetRole(ROLE_Authority);
	ASC = CreateDefaultSubobject<UAbilitySystemComponent>(TEXT("MyAwesomeComponent"));
	ASC->SetIsReplicated(true);
	ASC->SetReplicationMode(EGameplayEffectReplicationMode::Mixed);

Something must be up, because right here ASC->AbilityActorInfo is a nullptr and I have to create it explicitly. This does not happen in another class.

When I look inside the ASC with a debugger, I see that ActiveGameplayEffects has no owner set. Due to this, later on, when the ability is activated, during the handling of the cooldown effect, a call to ASC->ActivateGameplayEffects->Owner->GetWorld() fails, because Owner is a nullptr. This again, I just checked it, does not occur in the other class, which spawns the ASC component exactly as I posted it here.
Does anyone have an idea?

edit:
This is how I create the RTSItem objects

bool URTSInventoryComponent::AddItem(TSubclassOf<URTSSpell> ItemClass)
{
	for (uint8 Index = 0; Index < ItemSlots.Num(); Index++)
	{
		if (ItemSlots[Index] == nullptr)
		{
			ARTSItem* NewItem = NewObject<ARTSItem>(this, ARTSItem::StaticClass());
			NewItem->SetAbility(ItemClass, this->GetOwner());
			ItemSlots[Index] = NewItem;
			return true;
		}
	}
	return false;
}

[JFarrow (JohnF)]

What is the declaration of ASC? Is it a UPROPERTY?

[CoolRabi]

Yes, the complete declaration of RTSItem is

UCLASS(BlueprintType)
class CASTLEFIGHT_API ARTSItem : public AActor, public IAbilitySystemInterface, public ICommandGridInterface 
{
	GENERATED_BODY()
	
public:	
	// Sets default values for this actor's properties
	ARTSItem();
	ARTSItem(TSubclassOf<URTSSpell> Spell);

	UFUNCTION(BlueprintCallable)
	bool ActivateAbility();

	// Convenience member for some UI interfacing
	UPROPERTY()
	TSubclassOf<URTSSpell> AssociatedSpell;

	UPROPERTY(BlueprintReadOnly)
	UGameplayAbility* AssociatedAbility;

	UPROPERTY()
	TObjectPtr<UTexture2D> Icon;

	UPROPERTY()
	UAbilitySystemComponent* ASC;

	void SetAbility(TSubclassOf<URTSSpell> Spell, AActor* OuterOwner);

	UFUNCTION()
	virtual UTexture2D* GetIcon() override;

	virtual UAbilitySystemComponent* GetAbilitySystemComponent() const override;

	FGameplayAbilitySpecHandle AbilitySpecHandle;

	void SetupCombatComponent();

protected:
	// Called when the game starts or when spawned
	virtual void BeginPlay() override;

public:	
	// Called every frame
	virtual void Tick(float DeltaTime) override;

};

It is really weird. I know for a fact that the GAS in general works. I have a builder character who can use spells through his own AbilitySystemComponent. The setup in the builder character seems to be identical to what I am doing in the RTSItem class, but some pointers are null the ASC of RTSItem which are not null for the builder character’s ASC.

[CoolRabi]

Alright, I made it work. In the constructor, right after GetDefaultSubobject, I had to call

	ASC->RegisterComponent();

so that OnRegister() is called, where all the pointers are set that were missing. While this solves the crashes - I can now use proper cooldowns - I have a bad feeling about this. It should not be necessary to call RegisterComponent(). What could be the issue here that makes me have to do this?