Sorting works inconsistently , when table column contains null/undefined/empty values

I observed that the handlenulls method present in all sort methods(exmaple : alphasort) is working inconsistently. It is unable to handle the empty values in present in the table while sorting. Note - I am using Sort Ascending and Sort Descending options and not the header options.

Scenario - When a column containing null values is sorted -

1. Step 1 : Ascending order - null values are pushed at the bottom, values gets sorted correctly
2. Step 2 : Descending order - nothing happens ,sorting does not work.