Fix blank xfa rendering broken at f89acbc.
Fix blank xfa rendering broken at f89acbc.

One initializer was lost in that conversion.

R=weili@chromium.org

Review URL: https://codereview.chromium.org/1824173002 .

DrAlexx/pdfium,DrAlexx/pdfium,DrAlexx/pdfium,DrAlexx/pdfium