I have a site collection inside my SharePoint online tenant with the following url /sites/dev3/. I have the following code inside my Remote Event Receiver, where the RER get fired when items are added inside a custom list. Now i am creating a new sub-site under the site collection where i sub-site title will be equal to the list item title:-

private void HandleItemAdded(SPRemoteEventProperties properties)          {              using (ClientContext clientContext =                  TokenHelper.CreateRemoteEventReceiverClientContext(properties))              {                  if (clientContext != null)                  {                      try                      {                          List photos = clientContext.Web.Lists.GetById(                             properties.ItemEventProperties.ListId);                          ListItem item = photos.GetItemById(                             properties.ItemEventProperties.ListItemId);                          clientContext.Load(item);                          clientContext.ExecuteQuery();                            item["Title"] += "updated ";                            item.Update();                         WebCreationInformation creation = new WebCreationInformation();                         creation.Url = item["Title"].ToString();                         creation.Title = item["Title"].ToString();                         Web newWeb = clientContext.Web.Webs.Add(creation);                          // Retrieve the new web information.                          clientContext.Load(newWeb, w => w.Title);                         clientContext.ExecuteQuery();                           clientContext.ExecuteQuery();                      }                      catch (Exception oops)                      {                          System.Diagnostics.Trace.WriteLine(oops.Message);                      } 

but the above code will raise the following exeption:-

“The URL ‘/sites/dev3/testupdated ‘ is invalid. It may contain illegal characters, or be too long.”

so can anyone advice on this please?