Philip, there are different ways of doing this, but here's one that's fairly easy:
1. Duplicate the 'Job' field (this creates a calculated field with [Job] in it)
2. Put the 'Job (copy)' on the filter shelf
3. Edit the filter to exclude the Null
4. Put the original 'Job' field on the filter shelf
5. Show the Quick Filter
6. Click the triangle on the Quick Filter and select 'Only Relevant Values'
The Nulls disappear.
Thanks shawn for the help