From 544d2e26c7268325fddbc58e55a912e17b60f213 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@users.noreply.github.com>
Date: Thu, 6 Sep 2018 20:25:49 +0200
Subject: [PATCH] Fix NRE when VirtualizingStackPanel used with ItemsControl.

There is no `ScrollViewer` in the template for `ItemsControl` which means that if a `VirtualizingStackPanel` is used for `ItemsControl.ItemsPanel` then `InvalidateScroll` won't be set. Just do nothing in this case.

Fixes #1829.
---
 src/Avalonia.Controls/Presenters/ItemVirtualizer.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/Presenters/ItemVirtualizer.cs b/src/Avalonia.Controls/Presenters/ItemVirtualizer.cs
index c5344b29d9..46da8fe3f8 100644
--- a/src/Avalonia.Controls/Presenters/ItemVirtualizer.cs
+++ b/src/Avalonia.Controls/Presenters/ItemVirtualizer.cs
@@ -279,6 +279,6 @@ namespace Avalonia.Controls.Presenters
         /// <summary>
         /// Invalidates the current scroll.
         /// </summary>
-        protected void InvalidateScroll() => ((ILogicalScrollable)Owner).InvalidateScroll();
+        protected void InvalidateScroll() => ((ILogicalScrollable)Owner).InvalidateScroll?.Invoke();
     }
 }