MenuBar leaves trails when mounted in a Window

[tznind]

Describe the bug
When mounting a MenuBar in a Window you get a trail left behind where underlying window does not update itself to clear the old menu.

This seems to be the behaviour in both 1.8.2 nuget package and on develop.

Resizing the window clears the old 'trailing' state:

To Reproduce

Application.Init ();
MenuBar menubar;
MenuBarItem fileF9;
MenuItem runnewTask;
MenuItem exit;
MenuBarItem view;
MenuItem refreshNow;
MenuBarItem updateSpeed;
MenuItem high;
MenuItem normal;
MenuItem slow;
MenuItem paused;
var win = new Window ();
menubar = new Terminal.Gui.MenuBar ();
win.Width = Dim.Fill (0);
win.Height = Dim.Fill (0);
win.X = 0;
win.Y = 0;
win.Modal = false;
win.Text = "";
win.Border.BorderStyle = Terminal.Gui.BorderStyle.Single;
win.Border.BorderBrush = Terminal.Gui.Color.Blue;
win.Border.Effect3D = false;
win.Border.Effect3DBrush = null;
win.Border.DrawMarginFrame = true;
win.TextAlignment = Terminal.Gui.TextAlignment.Left;
win.Title = "Task Manager";
menubar.Width = Dim.Fill (0);
menubar.Height = 1;
menubar.X = 0;
menubar.Y = 0;
menubar.Data = "menubar";
menubar.Text = "";
menubar.TextAlignment = Terminal.Gui.TextAlignment.Left;
fileF9 = new Terminal.Gui.MenuBarItem ();
fileF9.Title = "_File (F9)";
runnewTask = new Terminal.Gui.MenuItem ();
runnewTask.Title = "Run new Task...";
runnewTask.Data = "RunnewTask";
runnewTask.Shortcut = ((Terminal.Gui.Key)(0u));
exit = new Terminal.Gui.MenuItem ();
exit.Title = "Exit";
exit.Data = "Exit";
exit.Shortcut = ((Terminal.Gui.Key)(0u));
fileF9.Children = new Terminal.Gui.MenuItem [] {
		runnewTask,
		exit};
view = new Terminal.Gui.MenuBarItem ();
view.Title = "View";
refreshNow = new Terminal.Gui.MenuItem ();
refreshNow.Title = "Refresh Now";
refreshNow.Data = "RefreshNow";
refreshNow.Shortcut = ((Terminal.Gui.Key)(0u));
updateSpeed = new Terminal.Gui.MenuBarItem ();
updateSpeed.Title = "Update Speed";
high = new Terminal.Gui.MenuItem ();
high.Title = "High";
high.Data = "High";
high.Shortcut = ((Terminal.Gui.Key)(0u));
normal = new Terminal.Gui.MenuItem ();
normal.Title = "Normal";
normal.Data = "Normal";
normal.Shortcut = ((Terminal.Gui.Key)(0u));
slow = new Terminal.Gui.MenuItem ();
slow.Title = "Slow";
slow.Data = "Slow";
slow.Shortcut = ((Terminal.Gui.Key)(0u));
paused = new Terminal.Gui.MenuItem ();
paused.Title = "Paused";
paused.Data = "Paused";
paused.Shortcut = ((Terminal.Gui.Key)(0u));
updateSpeed.Children = new Terminal.Gui.MenuItem [] {
		high,
		normal,
		slow,
		paused};
view.Children = new Terminal.Gui.MenuItem [] {
		refreshNow,
		updateSpeed};
menubar.Menus = new Terminal.Gui.MenuBarItem [] {
		fileF9,
		view};
win.Add (menubar);
Application.Run (win);