Guard against Scene being null in attachments it the wearing avatar is in the process of logging out.

OpenSim/Region/Framework/Scenes/SceneObjectGroup.cs

@@ -1886,6 +1886,8 @@ namespace OpenSim.Region.Framework.Scenes
             {
                 SceneObjectPart part = parts[i];
 
+                if (Scene != null)
+                {
                     Scene.ForEachRootScenePresence(delegate(ScenePresence avatar)
                     {
                         if (avatar.ParentID == LocalId)
@@ -1904,7 +1906,7 @@ namespace OpenSim.Region.Framework.Scenes
                         }
                     });
                 }
-
+            }
         }
 
         public void AddScriptLPS(int count)