Skip null values in Parallel Categories or Sankey diagram

I know this has been asked before, but from what I can find it hasn’t been answered yet.

Is it possible to ignore null values in a dataframe when plotting either a Parallel Categories plot or a Sankey diagram?

My data splits at a decision; one group continues with another decision while the other group terminates. My dataframe has null values present for the group that terminates. Is it possible to ignore them when I generate the plot, so there isn’t a path that goes from the last decision to a null decision?