Only take into account sprmTTableHeader if all previous rows had it.

Change-Id: I0f81da366c148963503b4aeba778f5d97aa72d26
Reviewed-on: https://gerrit.libreoffice.org/34931Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>