fix compiler warnings (GCC + Clang)

src/frontend/hud.cpp

@@ -310,7 +310,6 @@ void Hud::updateWorldGenDebug() {
 }
 
 void Hud::update(bool visible) {
-    const auto& level = frontend.getLevel();
     const auto& chunks = *player.chunks;
     const auto& menu = gui.getMenu();
 

src/frontend/menu.cpp

@@ -38,7 +38,6 @@ bool menus::call(Engine& engine, runnable func) {
     if (engine.isHeadless()) {
         throw std::runtime_error("menus::call(...) in headless mode");
     }
-    auto gui = engine.getGUI();
     try {
         func();
         return true;

src/frontend/screens/LevelScreen.cpp

@@ -154,7 +154,6 @@ void LevelScreen::saveDecorations() {
 void LevelScreen::saveWorldPreview() {
     try {
         logger.info() << "saving world preview";
-        const auto& paths = engine.getPaths();
         auto player = playerController->getPlayer();
         auto& settings = engine.getSettings();
         int previewSize = settings.ui.worldPreviewSize.get();