Use C++17 fallthrough

src/scrobbler/scrobblingapi20.cpp

@@ -178,7 +178,7 @@ void ScrobblingAPI20::Authenticate(const bool https) {
       messagebox_error.setTextFormat(Qt::RichText);
       messagebox_error.exec();
     }
-      // fallthrough
+      [[fallthrough]];
     case QMessageBox::Save:
       QApplication::clipboard()->setText(url.toString());
       break;