Error

Object reference not set to an instance of an object.
   at Volvo.CWP.SharePoint.GenericExtensions.Contains(IEnumerable collection, String lookfor, StringComparer comparer)
   at Volvo.CWP.SharePoint.Applications.Internet.CodeBehind.InternetPublishingPage.get_IsGoogleCrawler()
   at Volvo.CWP.SharePoint.Applications.Internet.CodeBehind.InternetPublishingPage.DisableRobots()
   at Volvo.CWP.SharePoint.Applications.Internet.CodeBehind.InternetPublishingPage.BuildDefaultMetaInfo()
   at Volvo.CWP.SharePoint.Applications.Internet.CodeBehind.InternetPublishingPage.Render(HtmlTextWriter writer)
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)