chore: add empty string guard (#2126)

Author: WilliamCunhaCardoso

packages/stripe_web/lib/src/web_stripe.dart

@@ -169,7 +169,7 @@ class WebStripe extends StripePlatform {
           paymentIntentClientSecret,
           data: stripe_js.ConfirmIdealPaymentData(
             paymentMethod: stripe_js.IdealPaymentMethodDetails.withBank(
-              ideal: stripe_js.IdealBankData(bank: paymentData.bankName),
+              ideal: stripe_js.IdealBankData(bank: paymentData.bankName ?? ""),
             ),
             returnUrl: urlScheme,
             // recommended
@@ -212,7 +212,7 @@ class WebStripe extends StripePlatform {
       paymentIntentClientSecret,
       data: stripe_js.ConfirmIdealPaymentData(
         paymentMethod: stripe_js.IdealPaymentMethodDetails.withBank(
-          ideal: stripe_js.IdealBankData(bank: paymentData.bankName),
+          ideal: stripe_js.IdealBankData(bank: paymentData.bankName ?? ""),
         ),
         returnUrl: returnUrl ?? urlScheme,
       ),