ui: set DO_NOTHING_ON_CLOSE close op prior to disposing

Disposed frames are still reachable via Window.getWindows() until gcd, and can
receive and process events. We don't want the splash screen to close the app if
it receives a window close event after being disposed.

runelite-client/src/main/java/net/runelite/client/ui/SplashScreen.java

@@ -30,7 +30,6 @@
 import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;
 import java.awt.image.BufferedImage;
-import java.io.IOException;
 import java.lang.reflect.InvocationTargetException;
 import javax.annotation.Nullable;
 import javax.swing.ImageIcon;
@@ -66,7 +65,7 @@ public class SplashScreen extends JFrame implements ActionListener
 	private volatile String subActionText = "";
 	private volatile String progressText = null;
 
-	private SplashScreen() throws IOException
+	private SplashScreen()
 	{
 		BufferedImage logo = ImageUtil.loadImageResource(SplashScreen.class, "runelite_transparent.png");
 
@@ -204,6 +203,12 @@ public static void stop()
 			}
 
 			INSTANCE.timer.stop();
+			// The CLOSE_ALL_WINDOWS quit strategy on MacOS dispatches WINDOW_CLOSING events to each frame
+			// from Window.getWindows. However, getWindows uses weak refs and relies on gc to remove windows
+			// from its list, causing events to get dispatched to disposed frames. The frames handle the events
+			// regardless of being disposed and will run the configured close operation. Set the close operation
+			// to DO_NOTHING_ON_CLOSE prior to disposing to prevent this.
+			INSTANCE.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
 			INSTANCE.dispose();
 			INSTANCE = null;
 		});