The setting is not there so it makes conditional null approach to filtering expressions (IE: IF( condition, value) ) not permissible in exactly the same way.
I was able to replicate the effect using the condition on the dimension , because there is a 'show nulls' checkbox there. (see below)
Other ways to filter out NULLs in the expression like set analysis will work too.
If there is a very specific technique or approach you are asking about...please post.