From d3b43efe161c3ff12cd8939cff6a821bbc8f94aa Mon Sep 17 00:00:00 2001
From: Dan Walmsley <dan@walms.co.uk>
Date: Thu, 29 Oct 2020 11:33:41 +0000
Subject: [PATCH] if TreeView has a selecteditem that isnt really part of the
 tree... then do not crash tab navigation.

---
 src/Avalonia.Controls/TreeView.cs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/Avalonia.Controls/TreeView.cs b/src/Avalonia.Controls/TreeView.cs
index b2bd5ab2e5..f020280496 100644
--- a/src/Avalonia.Controls/TreeView.cs
+++ b/src/Avalonia.Controls/TreeView.cs
@@ -378,10 +378,11 @@ namespace Avalonia.Controls
             {
                 if (!this.IsVisualAncestorOf(element))
                 {
-                    IControl result = _selectedItem != null ?
+                    var result = _selectedItem != null ?
                         ItemContainerGenerator.Index.ContainerFromItem(_selectedItem) :
                         ItemContainerGenerator.ContainerFromIndex(0);
-                    return (true, result);
+                    
+                    return (result is {}, result); // SelectedItem may not be in the treeview.
                 }
 
                 return (true, null);