Add default value for null column in laravel yajra table

Question

I use laravel yajra/datatables in my order model there is a one to many relations between driver and order in some cases the driver_id becomes NULL in cases so what i want to do is to print a default value in case if there is no driver for this order here is my OrderDataTable file

query method

public function query()
{   
   return Order::select('id', 'client_name', 'phone', 'price',  'shipping_price', 'city_id', 'status_id', 'driver_id')
     ->with('city:id,name')
     ->with('status:id,name')
     ->with('driver:id,name')
     ->orderBy('id', 'desc');
}

getColumns method

    protected function getColumns()
    {
        return [
            Column::make('client_name'),
            Column::make('phone'),
            Column::make('Price')->data('price'),
            Column::make('Shipping')->data('shipping_price')->name('shipping_price'),
            Column::make('City')->data('city.name')->name('city.name'),
            Column::make('Status')->data('status.name')->name('status.name'),
            Column::make('Driver')->data('driver.name')->name('driver.name'), // this is the column that i want to add default value for
            Column::computed('action')
                  ->exportable(false)
                  ->printable(false)
                  ->addClass('text-center'),
        ];
    }