Page Error

System.Web.HttpUnhandledException (0x80004005): Exception of type 'System.Web.HttpUnhandledException' was thrown. ---> System.ArgumentNullException: Value cannot be null.
Parameter name: String
at System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal)
at System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info)
at System.Int32.Parse(String s)
at SiteCountryProxy.CountryCount() in d:\wwwrootV4\HooverAuto\App_Code\Data\Proxy\SiteCountryProxy.cs:line 57
at Helper.initSiteSession() in d:\wwwrootV4\HooverAuto\App_Code\Utilities\Helper.cs:line 79
at MasterPage.Page_Init(Object sender, EventArgs e) in d:\wwwrootV4\HooverAuto\MasterPage.master.cs:line 18
at System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e)
at System.Web.UI.Control.OnInit(EventArgs e)
at System.Web.UI.UserControl.OnInit(EventArgs e)
at System.Web.UI.Control.InitRecursive(Control namingContainer)
at System.Web.UI.Control.InitRecursive(Control namingContainer)
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
at System.Web.UI.Page.HandleError(Exception e)
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
at System.Web.UI.Page.ProcessRequest()
at System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context)
at System.Web.UI.Page.ProcessRequest(HttpContext context)
at ASP.index_aspx.ProcessRequest(HttpContext context) in c:\windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\root\e96e7474\292eb8d0\App_Web_kaer5r2j.8.cs:line 0
at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)