Null values in Sankey chart

When playing around with the Sankey chart visualization, I was wondering if there was an option to hide links for null values. That would allow to show a funnel, where with each dimension the nodes sizes would be reduced. Of course I can exclude null values in the Data-Dimension section. However, that would filter the whole data set that is displayed.

I added an example. In the example, I would like to hide the links where the next node is empty. If I could color those links white, it would do the trick. However, I did not find how to do that.