From 981370f2159fe33b2ba99c237b9f9f74f9269841 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=88=98=E6=99=93=E9=9D=92?= <569132102@qq.com>
Date: Fri, 3 Jul 2020 13:43:57 +0800
Subject: [PATCH] ..

---
 .../Components/AvalonDock/Controls/LayoutDocumentPaneControl.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/source/Components/AvalonDock/Controls/LayoutDocumentPaneControl.cs b/source/Components/AvalonDock/Controls/LayoutDocumentPaneControl.cs
index 53944d2d..da2c900f 100644
--- a/source/Components/AvalonDock/Controls/LayoutDocumentPaneControl.cs
+++ b/source/Components/AvalonDock/Controls/LayoutDocumentPaneControl.cs
@@ -96,7 +96,7 @@ protected override void OnItemsChanged(NotifyCollectionChangedEventArgs e)
 			{
 				foreach (var item in e.OldItems)
 				{
-					if (item is LayoutContent layoutContent)
+					if (item is LayoutContent layoutContent && layoutContent.TabItem != null)
 					{
 						layoutContent.TabItem.Model = null;
 						layoutContent.TabItem.ContextMenu = null;