Fix blurry wallpaper when user locks on all apps surface

Bug: 242746421
Test: manual

TL;DR;;
setState toState= NORMAL called when locking screen on ALLAPPS screen
but mSurface==null
hence depth is not reset to NORMAL state

Change-Id: I26a37f7de8b0ecd481b36eebf07e1b79f8b0035c