HOTFIX: Trustwave Scan Issues Fixed

Fixed several issues found by Trustwave scans.
* Fixed null ref exception in ReportNavBar when attempting to access the session's User
* Moved the security check for the Google Checkout settings page up before any other logic when the page loads
* Store settings master page was erroring while building the breadcrumb trail when there was no Store ID specified, making it where some pages would not reach the security check. It was checking for null but the CurrentStore was a load on demand, and it was erroring in the load on demand.