Made application terminate when GameModeDialog is closed

src/dev/kske/chess/ui/GameModeDialog.java

@@ -1,6 +1,8 @@
 package dev.kske.chess.ui;
 
 import java.awt.FlowLayout;
+import java.awt.event.WindowAdapter;
+import java.awt.event.WindowEvent;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -35,6 +37,15 @@ public class GameModeDialog extends JDialog {
 		setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
 		getContentPane().setLayout(new FlowLayout(FlowLayout.CENTER, 5, 5));
 
+		// Exit application when the close button is pressed
+		addWindowListener(new WindowAdapter() {
+
+			@Override
+			public void windowClosing(WindowEvent evt) {
+				System.exit(0);
+			}
+		});
+
 		final BoardComponent	boardComponent		= boardPane.getBoardComponent();
 		final OverlayComponent	overlayComponent	= boardPane.getOverlayComponent();
 		final Board				board				= boardComponent.getBoard();