Function "revert to this version" doesn't work

none of the pages on my site have this functionality. instead i'm getting this message - see below. how do i fix it? thanks!

Server Error in '/' Application.

Object reference not set to an instance of an object.



Description: An unhandled exception occurred during
the execution of the current web request. Please review the stack trace
for more information about the error and where it originated in the
code.





Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.



Source Error:






Line 48: var sb = new StringBuilder();
Line 49: var actualCurrentNode = SiteMapBase.GetActualCurrentNode();
Line 50: var parentNode = (PageSiteNode)actualCurrentNode.ParentNode;
Line 51: var displaytitle = string.Empty;
Line 52:








Source File: D:\Annapolis20120925\UserControls\uc_sitepanelnavigation.ascx.cs    Line: 50




Stack Trace:






[NullReferenceException: Object reference not set to an instance of an object.]
SitefinityWebApp.UserControl.uc_sitepanelnavigation.BuildNavigation() in D:\Annapolis20120925\UserControls\uc_sitepanelnavigation.ascx.cs:50
SitefinityWebApp.UserControl.uc_sitepanelnavigation.Page_Load(Object sender, EventArgs e) in D:\Annapolis20120925\UserControls\uc_sitepanelnavigation.ascx.cs:40
System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14
System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35
System.Web.UI.Control.OnLoad(EventArgs e) +91
System.Web.UI.Control.LoadRecursive() +74
System.Web.UI.Control.LoadRecursive() +146
System.Web.UI.Control.LoadRecursive() +146
System.Web.UI.Control.LoadRecursive() +146
System.Web.UI.Control.LoadRecursive() +146
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2207











Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.272

Hi Inna,

It looks like the issue is originating from your custom navigation control: D:\Annapolis20120925\UserControls\uc_sitepanelnavigation.ascx.cs

Do you get this error only when trying to revert to a previous version or when you open the page for editing as well? 

Dear Inna

I had the same problem once and indead it was coused by me. I had removed a part that was used and therefore the page could not be reverted to the old version.

Markus