Prevent nearest touch frame nearest child crash when no children

NearestTouchFrame crashed because clickable children list was empty,
either there were no children inside the view group or most likely touch
event occured before onMeasure occurred. Fixed by returning early.

Bug: 112740585
Test: tap anywhere on the nav bar
Change-Id: Id0a805fbe039d9e774900e832cb75347f7a619de