Declare and set linksetdata to null when updating prims table where t…

…here is no linkdata on a prim. Previously it was left off an being explicitely set and the connector considers that an error.

OpenSim/Data/MySQL/MySQLSimulationData.cs

@@ -1632,6 +1632,10 @@ private void FillPrimCommand(MySqlCommand cmd, SceneObjectPart prim, UUID sceneG
             {
                 cmd.Parameters.AddWithValue("linksetdata", prim.SerializeLinksetData());
             }
+            else 
+            {
+                cmd.Parameters.AddWithValue("linksetdata", null);
+            }           
         }
 
         /// <summary>