Exception Thrown at me

Hi,
I’m writing a simple code but I’m getting a crash whenever I add a variable!? It’s complaining about the parent class “this is a nullptr”

Screenshot 2020-12-18 223045.png

not sure what to dubug at this point!

,h file


UCLASS()
class SPRUNGSTUDIOSTEST_CPP_API UMainMenu : public USST_UserWidget
{
GENERATED_BODY()

public:
UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Items")
int32 SlotAvailableAtIndex;

UFUNCTION()
void AddItemToInventory(FItemDetails ItemDetails);

UFUNCTION()
void AddNewItem(FItemDetails ItemDetails);


};

CPP file


#include "Menu/MainMenu.h"

void UMainMenu::AddItemToInventory(FItemDetails ItemDetails)
{
SlotAvailableAtIndex = 5;
UE_LOG(LogTemp, Warning, TEXT("Item has been added at %i"), SlotAvailableAtIndex);
}

void UMainMenu::AddNewItem(FItemDetails ItemDetails)
{
AddItemToInventory(ItemDetails);

Thanks in advance