Fix blur dropping for one frame while we transition away from bouncer

Bug: 391373459
Test: Verified manually.
 1. Repeatedly open and close bouncer
 2. Blur should transition smoothly without any 0 blur frames in between
Flag: com.android.systemui.bouncer_ui_revamp
Change-Id: Ia681b7234cac376b9c1a5f3854ac1c3d13c50664