duplicate sessions being added when making preference changes to a brand new
profile with existing data.
Preference changes trigger a reload, see PreferencesDialog::Save and
needs_reload, leading to MainWindow::reloadProfile -> MainWindow::CloseProfile
-> Profile::UnloadMachineData.
This is the root cause of the duplicate sessions, but the fact that it only
happened with newly created profiles, rather than on subsequent launches,
demonstrates an inconsistency in state of Profile. It should be identical when
initially created and when loaded via subsequent application launch.
Currently there is a very messy tangle of dependencies between
loaders, machines, sessions, and profiles. Right now the
simplest way to create a test loader instance is to create
a test profile, under which the machine and session instances
will exist.
