destroy() works on the Demo window

Signed-off-by: Jeff Carr <jcarr@wit.com>

infoTabUI.go

@@ -61,6 +61,12 @@ func makeCloudInfoBox() ui.Control {
 	})
 	vbox.Append(add4button, false)
 
+	add4abutton := ui.NewButton("Close Demo GUI")
+	add4abutton.OnClicked(func(*ui.Button) {
+		gui.CloseDemoUI()
+	})
+	vbox.Append(add4abutton, false)
+
 	// Send a protobuf Event over the WIT socket
 	add5button := ui.NewButton("Send protobuf to localhost")
 	add5button.OnClicked(func(*ui.Button) {