From b72f08354ab2adc203e5ebf27905c710dbe1a7d6 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 16 Oct 2015 00:23:19 +0200
Subject: [PATCH] Handle detached controls in layout pass.

Controls can still be queued for layout after they've been removed from
the visual tree.
---
 src/Perspex.Layout/LayoutManager.cs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Perspex.Layout/LayoutManager.cs b/src/Perspex.Layout/LayoutManager.cs
index 8b4e605fe4..f1c45693ab 100644
--- a/src/Perspex.Layout/LayoutManager.cs
+++ b/src/Perspex.Layout/LayoutManager.cs
@@ -276,12 +276,12 @@ namespace Perspex.Layout
                         {
                             var control = item.Control;
 
-                            while (control.PreviousArrange == null)
+                            while (control != null && control.PreviousArrange == null)
                             {
                                 control = control.GetVisualParent<ILayoutable>();
                             }
 
-                            if (control.GetVisualRoot() == Root)
+                            if (control != null && control.GetVisualRoot() == Root)
                             {
                                 control.Arrange(control.PreviousArrange.Value, true);
                             }