An exception occurred: read access violation. **this** was nullptr

I've just started to learn C++ developing a game using Unreal Engine 4.26.2.

I don't really know what I'm doing.

I have created an UMG.UserWidget to show the HUD.Then I have created a C++ class that inherits from UserWidget. After that, I have reparent blueprint to that UMG.UserWidget. I've done that because I want to get access this widget from C++ code (to update players scores).

Besides that I have a C++ class, which inherits from AHUD. I use this class to show the UMG.UserWidget with this code:

Custom C++ HUD Constructor

APongHUD::APongHUD()
{
    PlayerHudWidget = NewObject<UPlayerHUDWidget>(UPlayerHUDWidget::StaticClass());
    ConstructorHelpers::FClassFinder<UUserWidget> WBPPlayerHudFinder(TEXT("/Game/Blueprint/Widgets/UI/UMG_PlayerHUD"));
    if (WBPPlayerHudFinder.Succeeded())
    {
        HudClass = WBPPlayerHudFinder.Class;
    }
    else
    {
        PlayerHudWidget = nullptr;
    }
}

Begin Play

void APongHUD::BeginPlay()
{
    Super::BeginPlay();

    if (HudClass)
    {
        Widget = CreateWidget<UUserWidget>(GetWorld(), HudClass);

        Widget->AddToViewport();

        PlayerHudWidget = Cast<UPlayerHUDWidget>(Widget);
    }
}

I have tried this code with the line PlayerHudWidget = Cast<UPlayerHUDWidget>(Widget); and commenting it with the same error.

The problem appears when I try to change the scores with this function:

void APongHUD::SetAIScored(int value)
{
    if (PlayerHudWidget != nullptr)
    {
        PlayerHudWidget->SetAIScore(value);
    }
}

At this line if (PlayerHudWidget != nullptr) I get the error:

An exception occurred: read access violation. this was nullptr.

This is the UPlayerHUDWidget header file:

#pragma once

#include "CoreMinimal.h"
#include "Blueprint/UserWidget.h"
#include "PlayerHUDWidget.generated.h"

/**
 * 
 */
UCLASS()
class POMG_API UPlayerHUDWidget : public UUserWidget
{
    GENERATED_BODY()
    
public:
    UPROPERTY(BlueprintReadWrite, meta = (BindWidget))
    class UTextBlock* Player_Score;
    class UTextBlock* AI_Score;

    void SetPlayerScore(int NewScore);

    void SetAIScore(int NewScore);
};

And its implementation:

#include "PlayerHUDWidget.h"
#include "Components/TextBlock.h"

void UPlayerHUDWidget::SetPlayerScore(int NewScore)
{
    Player_Score->SetText(FText::AsNumber(NewScore));
}

void UPlayerHUDWidget::SetAIScore(int NewScore)
{
    AI_Score->SetText(FText::AsNumber(NewScore));
}

My problem is that I don't know how to update the UMG.UserWidget HUD from C++ and what I'm trying it doesn't work.

How can I update UMG.UserWidget HUD from C++? Maybe fixing this error.