fix minor race condition in SOP.SitTargetPositionLL where inconsistency could occur if the sit target position changed whilst the property was fetched

OpenSim/Region/Framework/Scenes/SceneObjectPart.cs

@@ -1146,7 +1146,7 @@ namespace OpenSim.Region.Framework.Scenes
         // the mappings more consistant.
         public Vector3 SitTargetPositionLL
         {
-            get { return new Vector3(m_sitTargetPosition.X, m_sitTargetPosition.Y,m_sitTargetPosition.Z); }
+            get { return m_sitTargetPosition; }
             set { m_sitTargetPosition = value; }
         }