Return early to prevent infinite recursion.

This is defensive code for bug b/376796346 whose repro is not available but it could block a partner launch. We log additional info to give us clues for the real root cause.
  Tests are added to check other highlevel functions to return defaults.

Test: By running atest pdf/framework/libs/pdfClient/
Flag: EXEMPT bugfix
Flag: EXEMPT bugfix b/379795444, b/376796346
Change-Id: I083c89a080878b409bfd8cc55803d0bfc5ae39bb