Fix compile warnings and errors from last commit, detected by clang.

src/gui/LauncherDialog.cxx

@@ -55,9 +55,7 @@ LauncherDialog::LauncherDialog(OSystem& osystem, DialogContainer& parent,
     myPattern(nullptr),
     myAllFiles(nullptr),
     myRomInfoWidget(nullptr),
-    mySelectedItem(0),
-    myStellaSettingsDialog(nullptr),
-    myOptionsDialog(nullptr)
+    mySelectedItem(0)
 {
   myUseMinimalUI = instance().settings().getBool("minimal_ui");
 
@@ -653,4 +651,4 @@ void LauncherDialog::openSettings()
         Menu::AppMode::launcher);
     myOptionsDialog->open();
   }
-}
+}

src/gui/StellaSettingsDialog.cxx

@@ -298,7 +298,7 @@ void StellaSettingsDialog::handleCommand(CommandSender* sender, int cmd,
 
     case GuiObject::kOKCmd:
       saveConfig();
-      // falls through
+      [[fallthrough]];
     case GuiObject::kCloseCmd:
       if (myMode != Menu::AppMode::emulator)
         close();

src/gui/StellaSettingsDialog.hxx

@@ -23,10 +23,10 @@ class PopUpWidget;
 #include "Props.hxx"
 #include "Menu.hxx"
 #include "Dialog.hxx"
+#include "MessageBox.hxx"
 
 namespace GUI {
   class Font;
-  class MessageBox;
 }
 
 class StellaSettingsDialog : public Dialog