of cells of blank rows.

This workaround is probably a fix for problems of most users, but for
a full solution it needs to extend the workaround for all rows with not
default settings, also avoiding of the possible performance problems.

Note: the number 1000 of the extra rows came from a similar workaround used in
XLSX export of Google Spreadsheets, but instead of listing extra empty 1000
rows in OOXML, this fix writes only the cells with not default settings from
the extra 1000 blank rows.

Change-Id: Icac9441b7eb1520dcd20fc04337e070d070591c7
Reviewed-on: https://gerrit.libreoffice.org/58575
Tested-by: Jenkins
Reviewed-by: László Németh <nemeth@numbertext.org>