Redirect crash

when loading the app webroot as an authenticated user, the client-side JS would redirect the browser to a specific error type, but still fire an AJAX request for the current error type ("undefined") prior to the reload concluding. This would attempt to open a readstream on a nonexistent db on the server in a way that caused a crash.

Fixed on client & server:
- inhibits AJAX request from firing if browser is redirecting
- checks that error type is not 'undefined' prior to loading leveldb