From b4a0317604b94fb6af8fa319eb63c0aabb63d681 Mon Sep 17 00:00:00 2001
From: yusuf-gunaydin <yusuf_tarik@hotmail.com>
Date: Sat, 6 Aug 2016 15:30:58 +0300
Subject: [PATCH] Fixed crash when undo is called on a TextBox with no changes.

---
 src/Avalonia.Controls/Utils/UndoRedoHelper.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/Utils/UndoRedoHelper.cs b/src/Avalonia.Controls/Utils/UndoRedoHelper.cs
index 7b88ade0ea..404b1e65da 100644
--- a/src/Avalonia.Controls/Utils/UndoRedoHelper.cs
+++ b/src/Avalonia.Controls/Utils/UndoRedoHelper.cs
@@ -37,7 +37,7 @@ namespace Avalonia.Controls.Utils
 
         public void Undo()
         {
-			if (_currentNode != null)  
+			if (_currentNode?.Previous != null)  
 			{
 				_currentNode = _currentNode.Previous;
 			}