Finish the implementation of GetUserInventory, even though it's still not used.

OpenSim/Services/HypergridService/HGInventoryService.cs

@@ -105,6 +105,12 @@ namespace OpenSim.Services.HypergridService
             return new List<InventoryFolderBase>();
         }
 
+        public override InventoryCollection GetUserInventory(UUID userID)
+        {
+            // NOGO for this inventory service
+            return null;
+        }
+
         public override InventoryFolderBase GetRootFolder(UUID principalID)
         {
             //m_log.DebugFormat("[HG INVENTORY SERVICE]: GetRootFolder for {0}", principalID);