Add page redirection logic to set up data directories when resuming a session if it wasn't set before

The logic to redirect users to the "Processing Parameters" page now works as intended. Additional logic now needs to be put in place for to set up data directories for the rsync threads to transfer files from.

Currently, if users close the window before setting the data directory, existing logic will direct users to the "Processing Parameters" page. In this event, no RsyncInstances are spawned, because no data directory was assigned to the session.