[SettingsLib] SegmentedButtonPreference fix NullPointerException when view is inflating

The ButtonGroup can not be empty, it will get NPE if all children's
visibility are GONE when inflating. So we should set all button's
visibility GONE and ButtonGroup visibility to GONE in xml, and turn on
ButtonGroup when the data is not empty.

Bug: 414319180
Test: manual
Flag: EXEMPT bug fix
Change-Id: Ib9c8cb2b7ddec8c22418ec6e0890cb9cf6280292