Bug 1074777 - If Loop server crashes, when trying to signing-up, we should inform the user about this fault

See bug https://bugzilla.mozilla.org/show_bug.cgi?id=1074777 please.
If we do the unique instance + lazy initialization thing we want need to create a new instance for each case, so you should be able to do `OfflineScreen.show(_('noConnection'));` here.