[Panlingual] App locales backup and restore

The delegate selector is a relatively new addition to backup and restore. If there is no backup in the source device, an attribute not found exception may occur when parsing the data during the restore process. Default value is provided for cases where the attribute is not found.

Bug: 343180989
Test: Manual test
Change-Id: Idb11da383a7a2387ebb3c6e3bbad873deb81a898