Fix issue with touches falling through nav bar in 3 button nav

- This fixes a regression from ag/17185260 where we are no longer
  returning early when computing the touchable region in different
  nav bar states.

Bug: 249053817
Test: Enable 3 button nav, dumpsys input and verify the touchable
      region matches the window frame
Change-Id: Ib5767494973bbb23b3125988b94dcf46a2a6df24