MailSettings: Convert `MailSettingsWidget` to a failable factory

Userland/Applications/MailSettings/MailSettingsWidget.cpp

@@ -36,13 +36,20 @@ void MailSettingsWidget::apply_settings()
     Config::write_string("Mail"sv, "User"sv, "Username"sv, m_email);
 }
 
-MailSettingsWidget::MailSettingsWidget()
+ErrorOr<NonnullRefPtr<MailSettingsWidget>> MailSettingsWidget::try_create()
+{
+    auto widget = TRY(adopt_nonnull_ref_or_enomem(new (nothrow) MailSettingsWidget()));
+    TRY(widget->setup());
+    return widget;
+}
+
+ErrorOr<void> MailSettingsWidget::setup()
 {
     // Common port values for email fetching
     m_common_ports.append("143");
     m_common_ports.append("993");
 
-    load_from_gml(mail_settings_widget_gml).release_value_but_fixme_should_propagate_errors();
+    TRY(load_from_gml(mail_settings_widget_gml));
 
     m_server_inputbox = *find_descendant_of_type_named<GUI::TextBox>("server_input");
     m_server_inputbox->set_text(Config::read_string("Mail"sv, "Connection"sv, "Server"sv, ""sv));
@@ -53,7 +60,7 @@ MailSettingsWidget::MailSettingsWidget()
     m_port_combobox = *find_descendant_of_type_named<GUI::ComboBox>("port_input");
     m_port_combobox->set_text(Config::read_string("Mail"sv, "Connection"sv, "Port"sv, "993"sv));
     m_port_combobox->set_only_allow_values_from_model(false);
-    m_port_combobox->set_model(*GUI::ItemListModel<DeprecatedString>::create(m_common_ports));
+    m_port_combobox->set_model(*TRY(GUI::ItemListModel<DeprecatedString>::try_create(m_common_ports)));
     m_port_combobox->on_change = [&](auto, auto) {
         set_modified(true);
     };
@@ -69,4 +76,6 @@ MailSettingsWidget::MailSettingsWidget()
     m_email_inputbox->on_change = [&]() {
         set_modified(true);
     };
+
+    return {};
 }

Userland/Applications/MailSettings/MailSettingsWidget.h

@@ -12,14 +12,17 @@
 #include <LibGUI/Window.h>
 
 class MailSettingsWidget final : public GUI::SettingsWindow::Tab {
-    C_OBJECT(MailSettingsWidget)
+    C_OBJECT_ABSTRACT(MailSettingsWidget)
 
 public:
+    static ErrorOr<NonnullRefPtr<MailSettingsWidget>> try_create();
+
     virtual void apply_settings() override;
     virtual void reset_default_values() override;
 
 private:
-    MailSettingsWidget();
+    MailSettingsWidget() = default;
+    ErrorOr<void> setup();
 
     DeprecatedString m_server;
     DeprecatedString m_port;