bnc#886540: Let's not push the available area down when no titles are there.

This improves visual layout compability with MS Office chart & looks better.

Change-Id: I348ea81152eca4e3bba9e0d9460448d9314738ad
(cherry picked from commit b398ed8e3f95b75705bb2e53d49589ef7fdbb1c7)
Reviewed-on: https://gerrit.libreoffice.org/10771
Reviewed-by: Matúš Kukan <matus.kukan@collabora.com>
Tested-by: Matúš Kukan <matus.kukan@collabora.com>