tdf#148111: docx std fields: use placeholder text for empty data
It is quite unexpected Word behavior: if data source for sdt field
exists but contains empty string it is not used. Placeholder is
inserted instead.
In general behavior is more complex: logic of replacement is defined
by <w:showingPlcHdr> property and results can vary (see testcase).
But LO does not support this property correctly yet.
Change-Id: I2ec8efe05f79a01af5d74d21bfcd05f3b19e3970
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/132096
Tested-by: Jenkins
Reviewed-by: Thorsten Behrens <thorsten.behrens@allotropia.de>
(cherry picked from commit
9d033508af5257aeebbd8c22a053db5e74a814d3)
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/132050
Reviewed-by: Xisco Fauli <xiscofauli@libreoffice.org>