Fix NPE from navbar touch cancel without down.

TouchInteractionService sends a touch cancel when the screen turns
off, for example. So we shouldn't assume there was a touch down.

Fix: 398855863
Test: NavHandleLongPressInputConsumerTest#testTouchCancelWithoutTouchDown
Flag: EXEMPT bugfix
Change-Id: Ic1b6e981fe183864663bd44e1488d6f6749183bc
2 files changed