[PIA] Fix NPE on rotate.

When you rotate/redraw the activity this view wouldn't necessarily
exist yet, so let's only act on it if it does.
[PSA] Minor refactor in handling Options

In these cases (doing something only when a view is guaranteed to be present),
we can more elegantly map on an Option[A], and avoid a pattern match.
[SA] Use onPostCreate here, nuke a race condition.