After I added I added shouldBeStrict to model raised error Undefined array key

In laravel 11 / livewire 3 / app I added shouldBeStrict to model :

class Currency extends Model implements HasMedia {

protected $table = 'currencies';
protected $primaryKey = 'id';
public $timestamps = false;

protected static function boot()
{
    parent::boot();
    if(App::isLocal()) {
        Model::shouldBeStrict();
    }
}

So now I can not use code like :

$currency->selected = true;

So I add 2 custom attributes in model :

protected $appends = ['select', 'mediaData'];

...


// Set select value.
public function setSelectAttribute(bool $value): void
{
    $this->attributes['select'] = $value;
}
// Get select value.
function getSelectAttribute()
{
    return $this->attributes['select'];   // ERROR POINTING TO THIS LINE
}


// Set mediaData value.
public function setMediaDataAttribute(array $value): void
{
    $this->attributes['mediaData'] = $value;
}
// Get mediaData value.
function getMediaDataAttribute(): array
{
    return $this->attributes['mediaData'];
}

But with first request to this model :

    foreach ($this->currencies as $currency) {
        var_dump($currency->select);
    }

I got error :

Undefined array key "select"

How to fix it ?

class Currency extends Model implements HasMedia
{
    protected $table = 'currencies';
    protected $primaryKey = 'id';
    public $timestamps = false;
    // Define custom attributes that should be appended to the model's JSON form
    protected $appends = ['select', 'mediaData'];
    // Internal variables to hold custom attribute values
    protected $customAttributes = [
        'select' => false, // Default value for `select`
        'mediaData' => [], // Default value for `mediaData`
    ];
    // Override the boot method for strict mode if in local environment
    protected static function boot()
    {
        parent::boot();
        if (App::isLocal()) {
            Model::shouldBeStrict();
        }
    }
    public function setSelectAttribute(bool $value): void
    {
        $this->customAttributes['select'] = $value;
    }
    public function getSelectAttribute()
    {
        return $this->customAttributes['select'] ?? false;
    }
    public function setMediaDataAttribute(array $value): void
    {
        $this->customAttributes['mediaData'] = $value;
    }

    // Get mediaData value (retrieve it from the custom attributes array)
    public function getMediaDataAttribute(): array
    {
        return $this->customAttributes['mediaData'] ?? [];
    }
}

Try this