Null doesn't match anything:
http://allenbrowne.com/casu-12.html
Consequently, if you put *anything* in the Criteria row under your field, it
excludes the Null values.
It is possible to craft a WHERE clause to return True if there's no match.
Post the WHERE clause of your query if you're stuck.
If you have several of these criteria, I find it easier to build the filter
clause using VBA code. Here's how:
Search form - Handle many optional criteria
at:
http://allenbrowne.com/ser-62.html
Just before the end of that article, there is an example of how to do it in
the query instead of via VBA if you really want to.
