From ee63773cd11cebeea4eba0a037b20676f96eb1fc Mon Sep 17 00:00:00 2001
From: Hixie <github.com@spam.hixie.ch>
Date: Wed, 1 Apr 2015 12:08:06 -0700
Subject: [PATCH] [Effen] fix _ensureDepth to work on root of tree, oops

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1050153002
---
 framework/fn.dart | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/framework/fn.dart b/framework/fn.dart
index 20a8b1cffac..e01c34ddbc4 100644
--- a/framework/fn.dart
+++ b/framework/fn.dart
@@ -94,8 +94,12 @@ abstract class UINode {
   int _nodeDepth;
   void _ensureDepth() {
     if (_nodeDepth == null) {
-      _parent.ensureDepth();
-      _nodeDepth = _parent._nodeDepth + 1;
+      if (_parent != null) {
+        _parent.ensureDepth();
+        _nodeDepth = _parent._nodeDepth + 1;
+      } else {
+        _nodeDepth = 0;
+      }
     }
   }