Merge to XFA: Remove dead code from CPDF_Metadata. Add missing nullptr check.

BUG=pdfium:117
R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1282653002 .

(cherry picked from commit 1e2ece0cf98f8daecdea5b45ebd20cedbcef4bd9)

Review URL: https://codereview.chromium.org/1274803004 .
3 files changed