Admin analytics query builder: null/not null select menu options not working

[GUI]

In the admin analytics interface, if you dive into the query builder, and then select "is null" or "is not null" for a specific field, the resulting query is currently broken.

This was accidentally broken by the fix to try to lower-case all the inputs by default: #205 However, I got a condition mixed up, which caused the code to try to downcase a null value, which triggered the error.

[GUI]

Fixed by NREL/api-umbrella-web#14