resolved fdo#78294 default null-date for document import is 1899-12-30

Change-Id: I9dfe76d422ad732a081442b95a995d8d395a098e
(cherry picked from commit 571cefca474e6b77d68f9fa31f805dcf692927fd)
Reviewed-on: https://gerrit.libreoffice.org/9253
Reviewed-by: Kohei Yoshida <libreoffice@kohei.us>
Tested-by: Kohei Yoshida <libreoffice@kohei.us>