Hot Exit: Support hot exit on empty workspaces

[Tyriar]

Hot exit (#101) should work on empty workspaces (those with no opened folder).

[Tyriar]

Restoring files in empty workspaces is probably a pre-requisite to this: #207

[Tyriar]

I looked into Electron's window ID, looks like it's 0 and incremented each time so we wouldn't be able to use that as a (empty) window identifier across sessions.