Ensure controller is attached before applying state

On devices that don't use the default SystemUI status bar, it's possible
that the StatusBarWindowController may not be attached. For this use
case, the current state should not be applied until it's attached, as
applying the state prior to this may cause NPE.

Bug: 218582429
Test: manual (gcar_emu_x86 && sdk_gphone_x86)
Change-Id: Ibe3c30ec8041dd5404c8a0def9a2a894362bf860