Add checkers and tests for empty locale in PNG file

match_locale() will return false for empty locale string in the PNG
file. Also add a manual test to validate if a PNG file is qualified to
use under recovery.

Bug: 34054052
Test: recovery_manual_test catches invalid PNG files successfully & Locale_test passed

Change-Id: Id7e2136e1d8abf20da15825aa7901effbced8b03