Merge pull request #2968 from AvaloniaUI/fix/scroll-to-view-crash

fix crash scrolling to view when clearing list.

src/Avalonia.Controls/Presenters/ItemVirtualizerSimple.cs

@@ -295,11 +295,14 @@ namespace Avalonia.Controls.Presenters
         /// <inheritdoc/>
         public override void ScrollIntoView(object item)
         {
-            var index = Items.IndexOf(item);
-
-            if (index != -1)
+            if (Items != null)
             {
-                ScrollIntoView(index);
+                var index = Items.IndexOf(item);
+
+                if (index != -1)
+                {
+                    ScrollIntoView(index);
+                }
             }
         }
 

src/Avalonia.Controls/Primitives/SelectingItemsControl.cs

@@ -1042,7 +1042,7 @@ namespace Avalonia.Controls.Primitives
                 RaiseEvent(e);
             }
 
-            if (AutoScrollToSelectedItem)
+            if (AutoScrollToSelectedItem && _selectedIndex != -1)
             {
                 ScrollIntoView(_selectedItem);
             }