[locale] avoid crash when there are no good locales

If the running locale doesn't match any locale in the list,
nothing is selected. Avoid a crash when referring to
first() of an empty list.

src/modules/locale/LCLocaleDialog.cpp

@@ -84,5 +84,6 @@ LCLocaleDialog::LCLocaleDialog( const QString& guessedLCLocale, const QStringLis
 QString
 LCLocaleDialog::selectedLCLocale()
 {
-    return m_localesWidget->selectedItems().first()->text();
+    const auto items = m_localesWidget->selectedItems();
+    return items.isEmpty() ? QString{} : items.first()->text();
 }