title: MVCSiteMapProvider crashed with null object
body: <p>I am using MvcSiteMapProvider to create menu for my web site. It was working properly but suddenly failed with error:</p>
  
  <p>System.NullReferenceException: Object reference not set to an instance of an object.</p>
  
  <p>and here is the stack trace:</p>
  
  <pre><code>[NullReferenceException: Object reference not set to an instance of an object.]
  
  MvcSiteMapProvider.AuthorizeAttributeAclModule.IsAccessibleToUser(IControllerTypeResolver controllerTypeResolver, DefaultSiteMapProvider provider, HttpContext context, SiteMapNode node) in c:\Projects\Codeplex\TFS10\mvcsitemap\Branches\3.1.0\src\MvcSiteMapProvider\MvcSiteMapProvider\AuthorizeAttributeAclModule.cs:80
     MvcSiteMapProvider.DefaultAclModule.IsAccessibleToUser(IControllerTypeResolver controllerTypeResolver, DefaultSiteMapProvider provider, HttpContext context, SiteMapNode node) in c:\Projects\Codeplex\TFS10\mvcsitemap\Branches\3.1.0\src\MvcSiteMapProvider\MvcSiteMapProvider\DefaultAclModule.cs:61
     MvcSiteMapProvider.DefaultSiteMapProvider.IsAccessibleToUser(HttpContext context, SiteMapNode node) in c:\Projects\Codeplex\TFS10\mvcsitemap\Branches\3.1.0\src\MvcSiteMapProvider\MvcSiteMapProvider\DefaultSiteMapProvider.cs:178
     System.Web.SiteMapNode.IsAccessibleToUser(HttpContext context) +17
     System.Web.StaticSiteMapProvider.GetChildNodes(SiteMapNode node) +378
     System.Web.SiteMapNode.get_ChildNodes() +30
     System.Web.SiteMapNode.get_HasChildNodes() +10
     MvcSiteMapProvider.Web.Html.MenuHelper.BuildModel(MvcSiteMapHtmlHelper helper, SiteMapNode startingNode, Boolean startingNodeInChildLevel, Boolean showStartingNode, Int32 maxDepth, Boolean drillDownToCurrent) in c:\Projects\Codeplex\TFS10\mvcsitemap\Branches\3.1.0\src\MvcSiteMapProvider\MvcSiteMapProvider\Web\Html\MenuHelper.cs:293
     MvcSiteMapProvider.Web.Html.MenuHelper.Menu(MvcSiteMapHtmlHelper helper, String templateName, SiteMapNode startingNode, Boolean startingNodeInChildLevel, Boolean showStartingNode, Int32 maxDepth, Boolean drillDownToCurrent) in c:\Projects\Codeplex\TFS10\mvcsitemap\Branches\3.1.0\src\MvcSiteMapProvider\MvcSiteMapProvider\Web\Html\MenuHelper.cs:234
     MvcSiteMapProvider.Web.Html.MenuHelper.Menu(MvcSiteMapHtmlHelper helper) in c:\Projects\Codeplex\TFS10\mvcsitemap\Branches\3.1.0\src\MvcSiteMapProvider\MvcSiteMapProvider\Web\Html\MenuHelper.cs:31
  </code></pre>
  
  <p>I cannot think of any changes I made to introduce this error. The only changes made were due to results by using StyleCop (e.g. alter order of usings, methods, properties, etc.). Any idea?</p>