fix ghost items

Author: timunie

src/Avalonia.Controls/VirtualizingStackPanel.cs

@@ -700,8 +700,21 @@ protected internal override int IndexFromContainer(Control container)
                 // hence the width extent should be correct now, and we can try to scroll again.
                 scrollToElement.BringIntoView();
 
-                _scrollToElement = null;
-                _scrollToIndex = -1;
+                // The layout pass normally adopts the temporary element into the realized range.
+                // When it doesn't (for example, while its containing pane has no usable width),
+                // it is still an internal child. Recycle it before dropping the reference so it
+                // cannot remain as a visible, unindexed "ghost" element.
+                if (_scrollToElement is { } unadoptedScrollToElement)
+                {
+                    var unadoptedScrollToIndex = _scrollToIndex;
+                    _scrollToElement = null;
+                    _scrollToIndex = -1;
+                    RecycleElement(unadoptedScrollToElement, unadoptedScrollToIndex);
+                }
+                else
+                {
+                    _scrollToIndex = -1;
+                }
                 return scrollToElement;
             }