Fix issue where we get stuck in DREAMING state

Occasionally WM may provide an empty or null array of apps to the
unocclude animation runner, which causes it to early exit. The logic
which triggers the transition out of the DREAM state was after that
early exit, causing the device to become stuck in the state. We instead
move that check to before the early exit. The call is a noop if the
device isn't dreaming.

Fixes: 405254417
Test: atest KeyguardViewMediatorTestKt
Flag: EXEMPT bugfix
Change-Id: I90d01e57f1211853a71dea625ae8cf60b377ca21