"Is Not" filter always excludes blanks

Here is a situation that comes up when using Data Slicer... I've got a list of people and they are either pursuing Degree 1, Degree 2, Degree 3 or their degree is blank. I want to exclude those pursuing Degree 1, so I add a filter for Degree "Is Not" Degree 1. Populi does not consider a blank degree to be a valid alternative to Degree 1 so the blanks get excluded as well. It would be nice if blanks were not automatically excluded, and perhaps there could be a separate option to exclude blanks.