$payment_method_type can be null in StripePaymentElement::canCapturePayment

Problem/Motivation

$payment_method_type can be null in StripePaymentElement::canCapturePayment

Proposed resolution

Turn

public function canCapturePayment(PaymentInterface $payment): bool {
  /** @var \Drupal\commerce_stripe\Plugin\Commerce\PaymentMethodType\StripePaymentMethodTypeInterface $payment_method_type */
  $payment_method_type = $payment->getPaymentMethod()?->getType();
  return $payment_method_type->canCapturePayment($payment);
}

into

public function canCapturePayment(PaymentInterface $payment): bool {
  $payment_method_type = $payment->getPaymentMethod()?->getType();
  if (!$payment_method_type instanceof StripePaymentMethodTypeInterface) {
    return FALSE;
  }

  return $payment_method_type->canCapturePayment($payment);
}