Resolves: tdf#117069 crash double clicking in certain chart

Change-Id: I4506a3517eff7f73cf793195e9d605d450b84fda
Reviewed-on: https://gerrit.libreoffice.org/58995
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

chart2/source/controller/main/ChartController.cxx

@@ -269,6 +269,9 @@ css::uno::Reference<css::chart2::XChartType> getChartType(
     Reference< chart2::XCoordinateSystemContainer > xCooSysContainer( xDiagram, uno::UNO_QUERY_THROW );
 
     Sequence< Reference< chart2::XCoordinateSystem > > xCooSysSequence( xCooSysContainer->getCoordinateSystems());
+    if (!xCooSysSequence.getLength()) {
+        return css::uno::Reference<css::chart2::XChartType>();
+    }
 
     Reference< chart2::XChartTypeContainer > xChartTypeContainer( xCooSysSequence[0], uno::UNO_QUERY_THROW );