Allow for null xModel in TitleHelper::getTitle

Witnessed a JunitTest_chart2_unoapi failure where (deep within Idle::Timeout)
chart::impl::ModelState::update is apparently called with a null xModel.  All
the code called from there appears to be careful to handle a null xModel, except
for chart::TitleHelper::getTitle, which---presumably by accident---stopped doing
so with 401f01caf5b357ac6c15b37a89c0a9aaeb46f4e4 "use ChartModel instead of
XModel in a few places."

Change-Id: I5788b5e41a6d68fe193cb214d736ee54c4c581d7
(cherry picked from commit 6acfc822566ca3c7d9fdd4af37ad5104a00d5d35)
Reviewed-on: https://gerrit.libreoffice.org/14126
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

0 files changed, 0 insertions, 0 deletions