[TD]fix misplaced section line

- BRepBndLib::Add results in wrong bbox center.
- replaced with BRepBndLib::AddOptimal

src/Mod/TechDraw/App/GeometryObject.cpp

@@ -772,7 +772,7 @@ Base::BoundBox3d GeometryObject::calcBoundingBox() const
     if (!edgeGeom.empty()) {
         for (BaseGeomPtrVector::const_iterator it( edgeGeom.begin() );
                 it != edgeGeom.end(); ++it) {
-             BRepBndLib::Add((*it)->occEdge, testBox);
+             BRepBndLib::AddOptimal((*it)->occEdge, testBox);
         }
     }
     
@@ -937,9 +937,9 @@ gp_Pnt TechDraw::findCentroid(const TopoDS_Shape &shape,
     BRepBuilderAPI_Transform builder(shape, tempTransform);
 
     Bnd_Box tBounds;
-    BRepBndLib::Add(builder.Shape(), tBounds);
-
     tBounds.SetGap(0.0);
+    BRepBndLib::AddOptimal(builder.Shape(), tBounds, true, false);
+
     Standard_Real xMin, yMin, zMin, xMax, yMax, zMax;
     tBounds.Get(xMin, yMin, zMin, xMax, yMax, zMax);