Fix crash when adding items to BottomNavigationView.

BottomNavigationView would crash when trying to add items without calling
menu inflation first as it was did not initialize the menu object correctly
in such case.

Bug: 32325084
Test: added BottomNavigationViewTest#testAddItemsWithoutMenuInflation that
      now passes with my patch.

Change-Id: Id7597d38596f1e55b1dea1b1ff699868101381e4
3 files changed