@@ -111,18 +111,21 @@ private static void RegisterNewObjects(List<Object> newHierarchy, List<Object> h
 
             foreach (var i in newHierarchy)
             {
-                var found = false;
-                foreach (var j in hierarchy)
+                if (i != null)
                 {
-                    if (j.GetInstanceID() == i.GetInstanceID())
+                    var found = false;
+                    foreach (var j in hierarchy)
                     {
-                        found = true;
-                        break;
+                        if (j != null && j.GetInstanceID() == i.GetInstanceID())
+                        {
+                            found = true;
+                            break;
+                        }
+                    }
+                    if (!found)
+                    {
+                        danglingObjects.Add(i);
                     }
-                }
-                if (!found)
-                {
-                    danglingObjects.Add(i);
                 }
             }
 
 
@@ -1,4 +1,4 @@
-## Unity 2017.4.17f1 C# reference source code
+## Unity 2017.4.18f1 C# reference source code
 
 The C# part of the Unity engine and editor source code.
 May be used for reference purposes only.
Original file line number	Diff line number	Diff line change
`@@ -111,18 +111,21 @@ private static void RegisterNewObjects(List<Object> newHierarchy, List<Object> h`
`111`	`111`
`112`	`112`	`foreach (var i in newHierarchy)`
`113`	`113`	`{`
`114`		`- var found = false;`
`115`		`- foreach (var j in hierarchy)`
	`114`	`+ if (i != null)`
`116`	`115`	`{`
`117`		`- if (j.GetInstanceID() == i.GetInstanceID())`
	`116`	`+ var found = false;`
	`117`	`+ foreach (var j in hierarchy)`
`118`	`118`	`{`
`119`		`- found = true;`
`120`		`- break;`
	`119`	`+ if (j != null && j.GetInstanceID() == i.GetInstanceID())`
	`120`	`+ {`
	`121`	`+ found = true;`
	`122`	`+ break;`
	`123`	`+ }`
	`124`	`+ }`
	`125`	`+ if (!found)`
	`126`	`+ {`
	`127`	`+ danglingObjects.Add(i);`
`121`	`128`	`}`
`122`		`- }`
`123`		`- if (!found)`
`124`		`- {`
`125`		`- danglingObjects.Add(i);`
`126`	`129`	`}`
`127`	`130`	`}`
`128`	`131`
Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		`-## Unity 2017.4.17f1 C# reference source code`
	`1`	`+## Unity 2017.4.18f1 C# reference source code`
`2`	`2`
`3`	`3`	`The C# part of the Unity engine and editor source code.`
`4`	`4`	`May be used for reference purposes only.`