Bug: searching users by blank email gives back a user with an email

In our test environment we noticed that when calling GET /api/v2/users/search?query=email: (that is to say, with a blank email) it returns a user with an email. 

This doesn't seem intentional, I would expect a 400 error (or a list of users with no email, although I imagine it'd be better to have that functionality under a more explicit search string such as email:null or something).