coverity#1158136 Unchecked dynamic_cast

Change-Id: I8d4e7c497430faacd0d8f1138b9af8b2f11127a0

chart2/source/controller/dialogs/dlg_ObjectProperties.cxx

@@ -189,6 +189,7 @@ void ObjectPropertiesDialogParameter::init( const uno::Reference< frame::XModel
                     if( m_bIsCrossingAxisIsCategoryAxis )
                     {
                         ChartModel* pModel = dynamic_cast<ChartModel*>(xChartModel.get());
+                        if (pModel)
                             m_aCategories = DiagramHelper::getExplicitSimpleCategories( *pModel );
                     }
                 }
@@ -197,11 +198,14 @@ void ObjectPropertiesDialogParameter::init( const uno::Reference< frame::XModel
                 if ( nDimensionIndex == 0 && aData.AxisType == chart2::AxisType::CATEGORY )
                 {
                     ChartModel* pModel = dynamic_cast<ChartModel*>(xChartModel.get());
+                    if (pModel)
+                    {
                         ExplicitCategoriesProvider aExplicitCategoriesProvider( xCooSys, *pModel );
                         m_bComplexCategoriesAxis = aExplicitCategoriesProvider.hasComplexCategories();
                     }
                 }
             }
+        }
 
         //no staggering of labels for 3D axis
         m_bCanAxisLabelsBeStaggered = nDimensionCount==2;