BI Publisher 'first' and 'last' column summary functions grab null values

As the title suggests, I have discovered that the 'first' column summary function will always grab the first value, regardless of if that value is null or not. Same with the 'last' function. Compare this to the behavior of Oracle Reports where the first/last function grabs the first/last non-null value. Is there a way to change the default behavior of these functions, or ideally change it on a case-by-case basis for each data model?