Merge pull request #2236 from AkiSakurai/NoAddChildWindow

Do not add child window to parent when the child window is in the TabbedWindows of parent

src/Eto.Mac/Forms/MacWindow.cs

@@ -1257,7 +1257,7 @@ bool InternalSetOwner(Window owner)
 				if (owner != null)
 				{
 					var macWindow = owner.Handler as IMacWindow;
-					if (macWindow != null)
+					if (macWindow != null && macWindow.Control.TabbedWindows?.Contains(Control) != true)
 					{
 						macWindow.Control.AddChildWindow(Control, NSWindowOrderingMode.Above);
 						OnSetAsChildWindow();