Add override to MapPolygonNode/MapPolylineNode::isSubtreeBlocked

Change-Id: I30ffbe559af8cf911a3525b578a875b5dab69c51
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

src/location/declarativemaps/qdeclarativepolygonmapitem_p.h

@@ -148,7 +148,7 @@ public:
                 const QGeoMapItemGeometry *fillShape,
                 const QGeoMapItemGeometry *borderShape);
 
-    bool isSubtreeBlocked() const;
+    bool isSubtreeBlocked() const override;
 
 private:
     QSGFlatColorMaterial fill_material_;

src/location/declarativemaps/qdeclarativepolylinemapitem_p.h

@@ -185,7 +185,7 @@ public:
     ~MapPolylineNode();
 
     void update(const QColor &fillColor, const QGeoMapItemGeometry *shape);
-    bool isSubtreeBlocked() const;
+    bool isSubtreeBlocked() const override;
 
 private:
     QSGFlatColorMaterial fill_material_;