Test has been refactored into 2 tests.

Removed test that has been refactored into 2 separate tests. Thanks
@donandren for finding those bugs!

tests/Avalonia.Controls.UnitTests/ListBoxTests.cs

@@ -234,43 +234,6 @@ namespace Avalonia.Controls.UnitTests
             target.Arrange(new Rect(0, 0, 100, 100));
         }
 
-        [Fact]
-        public void ListBox_Set_SelectedItem_Should_Not_Crash_bug589_bug591()
-        {
-            using (UnitTestApplication.Start(TestServices.StyledWindow))
-            {
-                var items = new[] { "Foo", "Bar", "Baz " };
-                var target = new ListBox
-                {
-                    Template = ListBoxTemplate()
-                };
-
-                Prepare(target);
-
-                //emulate control is not in foreground or not visible
-                //also control can be child of  parent with size 0,0
-                //that's real case scenario although it looks bit unreal
-                target.Measure(new Size(0, 0));
-                target.Arrange(new Rect(0, 0, 0, 0));
-
-                target.Items = items;
-
-                //bug #591 in ItemVirtualizerSimple.cs:line 471
-                //var container = generator.ContainerFromIndex(index); <- here container is null
-                //and NullReferenceException will be raised if LayoutManager is not null
-                //line 482 
-                //if (!new Rect(panel.Bounds.Size).Contains(container.Bounds)) <- this check will fail
-
-                //bug #589 - currently this unit test is failing with
-                //IndexOutOfRangeException 
-                // in CreateAndRemoveContainers() ItemVirtualizerSimple.cs:line 274
-                //generator.Materialize(index, Items.ElementAt(index), memberSelector); <- index is -1
-                target.SelectedItem = items.First();
-
-                Assert.Equal(items.First(), target.SelectedItem);
-            }
-        }
-
         private class Item
         {
             public Item(string value)