Transition to signin with error message on invalid token not 500 error screen

closes #3548
- Add error to hidenav, removes menubar from error screen.
- Wrap atob() in a try/catch
- Added regex to try and validate if params.token at least looks like base64
Merge pull request #3629 from shindakun/500error

Transition to signin with error message on invalid token not 500 error