P: Smart albums to show missing metadata fields

A smart album to show metadata fields that are empty would be very helpful.  For example, a smart album that shows which photos do not have gps information or do not have anything in the location field.

I assign full location information to my photographs.  The majority of my photos imported into Lightroom desktop have gps information in the metadata.  Lightroom will automatically assign information to the Country, City and State/Provence fields using the gps coordinates.  I type information into the Location field.  Occasionally gps data is not assigned.  It would be very helpful to be able to quickly identify photographs where the gps and location fields are empty rather than going through them one by one.