Feature Request: Add "None" option to filter dropdowns

[PhillyPhotog-ops]

Add a "None" option to the filter drop-downs. Currently, you can select any of the stored values, but there is no way to find models that are untagged, don't have a license, don't have a parent model, or are missing the designer.

[jefferose]

Unless it's a version difference or I'm missing something, TAGS are the only one that don't have this. I asked for this a long time ago and it was added.