fix: prevent users from selecting null as a country during signup

Co-authored-by: nig <nig@tutao.de>

src/common/gui/base/GuiUtils.ts

@@ -57,13 +57,7 @@ export function renderCountryDropdown(params: {
 	return m(DropDownSelector, {
 		label: params.label ?? "invoiceCountry_label",
 		helpLabel: params.helpLabel,
-		items: [
-			...dropdownCountries(),
-			{
-				value: null,
-				name: lang.get("choose_label"),
-			},
-		],
+		items: [...dropdownCountries(), { value: null, name: lang.get("choose_label"), selectable: false }],
 		selectedValue: params.selectedCountry,
 		selectionChangedHandler: params.onSelectionChanged,
 	})

src/common/subscription/InvoiceAndPaymentDataPage.ts

@@ -123,7 +123,8 @@ export class InvoiceAndPaymentDataPage implements WizardPageN<UpgradeSubscriptio
 								disabled:
 									(this._selectedPaymentMethod() === PaymentMethodType.CreditCard &&
 										this.ccViewModel.validateCreditCardPaymentData() != null) ||
-									(this._selectedPaymentMethod() === PaymentMethodType.Paypal && !this.isPaypalLinked()),
+									(this._selectedPaymentMethod() === PaymentMethodType.Paypal && !this.isPaypalLinked()) ||
+									this._invoiceDataInput?.selectedCountry() == null,
 							}),
 						),
 					]

src/common/subscription/giftcards/RedeemGiftCardWizard.ts

@@ -441,6 +441,7 @@ class RedeemGiftCardPage implements WizardPageN<RedeemGiftCardModel> {
 							.catch(ofClass(UserError, showUserError))
 							.catch(ofClass(CancelledError, noOp))
 					},
+					disabled: !this.confirmed || this.country == null,
 				}),
 			),
 		])