Open Contour Plots - Overlaid Contour Plot from learning center.
Highlight col(C) and col(D), select plot: contour,heatmap: overlaid contour plot.
==>Contour levels:Low-High branch is folded
Expand the branch.
-->all 4 eidtbox is empty.
==>ok button is enabled, we should show error msg and disable ok button.
Click ok.
==>no plot show in new created graph.