From 377cf89824f11150c3caa41adb09fb2f6f3df633 Mon Sep 17 00:00:00 2001
From: Bob Arnson <bob@joyofsetup.com>
Date: Wed, 22 Aug 2018 19:49:07 -0400
Subject: Prevent crash when non-advertised Class omits Context. Fixes #5651.

---
 src/WixToolset.Core/Compiler.cs | 33 ++++++++++++++++++---------------
 1 file changed, 18 insertions(+), 15 deletions(-)

(limited to 'src/WixToolset.Core/Compiler.cs')

diff --git a/src/WixToolset.Core/Compiler.cs b/src/WixToolset.Core/Compiler.cs
index 437c1481..a4c289f7 100644
--- a/src/WixToolset.Core/Compiler.cs
+++ b/src/WixToolset.Core/Compiler.cs
@@ -1097,24 +1097,27 @@ namespace WixToolset.Core
             }
 
             HashSet<string> uniqueContexts = new HashSet<string>();
-            foreach (string context in contexts)
+            if (contexts != null)
             {
-                if (uniqueContexts.Contains(context))
-                {
-                    this.Core.Write(ErrorMessages.DuplicateContextValue(sourceLineNumbers, context));
-                }
-                else
+                foreach (string context in contexts)
                 {
-                    uniqueContexts.Add(context);
-                }
+                    if (uniqueContexts.Contains(context))
+                    {
+                        this.Core.Write(ErrorMessages.DuplicateContextValue(sourceLineNumbers, context));
+                    }
+                    else
+                    {
+                        uniqueContexts.Add(context);
+                    }
 
-                if (context.EndsWith("32", StringComparison.Ordinal))
-                {
-                    class32bit = true;
-                }
-                else
-                {
-                    class16bit = true;
+                    if (context.EndsWith("32", StringComparison.Ordinal))
+                    {
+                        class32bit = true;
+                    }
+                    else
+                    {
+                        class16bit = true;
+                    }
                 }
             }
 
-- 
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