From 485bd77c0c69431cb369174c14100bef469c67ff Mon Sep 17 00:00:00 2001
From: John Lewin <lewin76@gmail.com>
Date: Mon, 3 Sep 2018 16:39:43 -0700
Subject: [PATCH] Guard for null

- Issue MatterHackers/MCCentral#4090
Help fails to open due to null value in dictionary lookup
---
 SetupWizard/HelpPage.cs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/SetupWizard/HelpPage.cs b/SetupWizard/HelpPage.cs
index d4c36e8f9..0125a886e 100644
--- a/SetupWizard/HelpPage.cs
+++ b/SetupWizard/HelpPage.cs
@@ -332,7 +332,8 @@ namespace MatterHackers.MatterControl
 					};
 
 					if (item.Name == guideKey
-						|| (item.ArticleKey == guideKey
+						|| (guideKey != null
+							&& item.ArticleKey == guideKey
 							&& ApplicationController.Instance.HelpArticlesByID.ContainsKey(guideKey)))
 					{
 						initialSelection = newNode;