From b2414c1ab87a4bdc0e192fe4d9c2f4573d8a188a Mon Sep 17 00:00:00 2001
From: Sebastiaan Janssen <sebastiaan@umbraco.com>
Date: Tue, 26 Mar 2013 09:33:08 -0100
Subject: [PATCH 1/2] Fixes U4-1987 Error when attempting to save document type

---
 src/umbraco.cms/businesslogic/ContentType.cs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/umbraco.cms/businesslogic/ContentType.cs b/src/umbraco.cms/businesslogic/ContentType.cs
index 2154ec0118..bd136b1b44 100644
--- a/src/umbraco.cms/businesslogic/ContentType.cs
+++ b/src/umbraco.cms/businesslogic/ContentType.cs
@@ -144,7 +144,8 @@ namespace umbraco.cms.businesslogic
                 }
                 foreach (Tuple<string, string> key in toDelete)
                 {
-                    _propertyTypeCache.Remove(key);
+                    if(_propertyTypeCache.ContainsKey(key))
+                        _propertyTypeCache.Remove(key);
                 }				
             }
 			//don't put lock around this as it is ConcurrentDictionary.

From ff961abaabd15f2239ca29cd63c29d203b6b7eac Mon Sep 17 00:00:00 2001
From: Sebastiaan Janssen <sebastiaan@umbraco.com>
Date: Tue, 26 Mar 2013 09:50:48 -0100
Subject: [PATCH 2/2] Actual fix for U4-1987 Error when attempting to save
 document type

---
 src/umbraco.cms/businesslogic/ContentType.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/umbraco.cms/businesslogic/ContentType.cs b/src/umbraco.cms/businesslogic/ContentType.cs
index bd136b1b44..073324fa96 100644
--- a/src/umbraco.cms/businesslogic/ContentType.cs
+++ b/src/umbraco.cms/businesslogic/ContentType.cs
@@ -144,7 +144,7 @@ namespace umbraco.cms.businesslogic
                 }
                 foreach (Tuple<string, string> key in toDelete)
                 {
-                    if(_propertyTypeCache.ContainsKey(key))
+                    if(_propertyTypeCache != null)
                         _propertyTypeCache.Remove(key);
                 }				
             }