Compare Tables with nulls in groups. 

I have a compare table  and when I add a column to group by that has null values, any rows that have a null value in the column get dropped. 

Is there something in the compare table step JSON so it keeps rows with the nulls in one of the group by column. 

I have a similiarly grouped SAQL step and it will happily group the null values in those columns. 

This is resulting in the compare table showing no results where as every other widget on the dashboard is showing results.