Grid Statistics Histogram: make sure reloading project works.

ApplicationLibCode/ProjectDataModel/Histogram/RimGridStatisticsHistogramDataSource.h

@@ -52,6 +52,7 @@ protected:
     QList<caf::PdmOptionItemInfo> calculateValueOptions( const caf::PdmFieldHandle* fieldNeedingOptions ) override;
     void                          defineUiOrdering( QString uiConfigName, caf::PdmUiOrdering& uiOrdering ) override;
     void fieldChangedByUi( const caf::PdmFieldHandle* changedField, const QVariant& oldValue, const QVariant& newValue ) override;
+    void initAfterRead() override;
 
     RigHistogramData createStatisticsData() const;