Rails Devise Requires Email

I have seen many threads on them, however none solved the issue for me (other people's issues were solved). I am trying to sign in via username password and no email, but I get

SELECT "users".* FROM "users" WHERE "users"."email" IS NULL LIMIT 1

Here is my code:

class User < ActiveRecord::Base
 #devise :omniauthable
 include DeviseTokenAuth::Concerns::User
 devise :authentication_keys => [:username]
end

In devise.rb:

config.confirmation_keys = [ :username ]
config.authentication_keys = [ :username ]
config.case_insensitive_keys = [ :username ]
config.strip_whitespace_keys = [ :username ]

I have really no idea where the error could be..