How to include "NULL" object in query or filter

I am doing a query and or filter on “Resolution” field

If the state is in a specific type the resolution field shows as a “-“ meaning nothing is set.

 Example:

if the workitem is in a state of submitted there is no resolution... 

when you look at the results from a query the resolution field shows a "-"

If you look at the oslc the resolution field is completely blank

How do I include those that are blank in a filter? Basically include null?

ive tried resolution/name != "Withdrawn" (this returns all the items that match that except the ones that are null...

Or, can you generate a javascript to query it?