message: Provide a default empty string for menu item on Android.
diff: @@ -164,7 +164,9 @@ public class NavigationBarView extends AppBarLayout {
  if (menuItemProps == null) {
  continue;
  }
  - String title = menuItemProps.getString(PROP_ACTION_TITLE);
  + String title = menuItemProps.hasKey(PROP_ACTION_TITLE)
  + ? menuItemProps.getString(PROP_ACTION_TITLE)
  + : "";
  ReadableMap iconSource = menuItemProps.getMap(PROP_ACTION_ICON);
  MenuItem menuItem = toolbar.getMenu().add(Menu.NONE, Menu.NONE, i, title);
  if (iconSource != null) {
  