fdo#81102: fix .doc import of blank even page header

Honour the "different odd & even pages" header/footer setting from the
doc file even if there is no content for an even page header or footer.

Conflicts:
	sw/qa/extras/ww8import/ww8import.cxx
Reviewed on:
	https://gerrit.libreoffice.org/10191

Change-Id: I963f7f7189e399b1d859db0788fbfd291e868c54