Fix navigation input consumer not working when first window is invisible

The nav InputConsumer should be the top window without being related
to some window or it may be hidden if the window is not visible.

Test: atest com.android.server.wm
Test: atest WindowInsetsControllerTests
Bug: 167940326
Change-Id: I842114e68eaedaa008972a0a84c6b6394174f232