Fix wrong conversion to QVariant

It was converted to bool-like type which is wrong.

src/gui/optionsdialog.cpp

@@ -1638,7 +1638,7 @@ void OptionsDialog::setLocale(const QString &localeStr)
     if (index < 0)
     {
         // Unrecognized, use US English
-        index = m_ui->comboI18n->findData(u"en", Qt::UserRole);
+        index = m_ui->comboI18n->findData(u"en"_qs, Qt::UserRole);
         Q_ASSERT(index >= 0);
     }
     m_ui->comboI18n->setCurrentIndex(index);