Forum Error

System.Web.HttpUnhandledException (0x80004005): Exception of type 'System.Web.HttpUnhandledException' was thrown. ---> System.ArgumentNullException: obj cannot be null
Parameter name: obj
   at YAF.Types.CodeContracts.VerifyNotNull[T](T obj) in C:\inetpub\wwwroot\YAFNET-3_1_13_source\yafsrc\YAF.Types\CodeContracts.cs:line 50
   at YAF.Web.Extensions.PageLinkExtensions.AddCategory(List`1 pageLinks, Category category)
   at YAF.Pages.DeleteMessage.CreatePageLinks()
   at YAF.Core.BasePages.ForumPage.ForumPage_Load(Object sender, EventArgs e)
   at System.EventHandler.Invoke(Object sender, EventArgs e)
   at System.Web.UI.Control.OnLoad(EventArgs e)
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.<LoadRecursiveAsync>d__246.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Util.WithinCancellableCallbackTaskAwaitable.WithinCancellableCallbackTaskAwaiter.GetResult()
   at System.Web.UI.Page.<ProcessRequestMainAsync>d__523.MoveNext()
   at System.Web.UI.Page.HandleError(Exception e)
   at System.Web.UI.Page.<ProcessRequestMainAsync>d__523.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Util.WithinCancellableCallbackTaskAwaitable.WithinCancellableCallbackTaskAwaiter.GetResult()
   at System.Web.UI.Page.<ProcessRequestAsync>d__515.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.UI.Page.<ProcessRequestAsync>d__554.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.TaskAsyncHelper.EndTask(IAsyncResult ar)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step)
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)