Stop an exception being thrown and a teleport/border cross failing if the desintation sim has no active script engines.

This involves getting IScene.RequestModuleInterfaces() to return an empty array (as was stated in the method doc) rather than an array containing one null entry.
Callers adjusted to stop checking for the list reference being null (which never happened anyway)

OpenSim/Region/Framework/Scenes/SceneBase.cs

@@ -449,7 +449,7 @@ namespace OpenSim.Region.Framework.Scenes
             }
             else
             {
-                return new T[] { default(T) };
+                return new T[] {};
             }
         }