ErrorException Trying to access array offset on value of type null

[Shayboniyshoh]

public function handle($event)

{

    $couponName = session()->get('coupon')['name'];

    if ($couponName) {

        $coupon = Coupon::where('code', $couponName)->first();

        dispatch_now(new UpdateCoupon($coupon));

    }

}

I have following error when I click to "Add To Cart" button: ErrorException Trying to access array offset on value of type null.

it points me to the following line of code which I pasted above, and it is the peace of code inside CardUpdateListener.php:$couponName = session()->get('coupon')['name'];

[Martin-1182]

$couponName = session()->get('coupon')['name'] ?? null;