devise first_name can't be blank when it's not
#You need to add them to the strong params for the devise controller.
#You can create your own (Which extend Devise) and then:
class RegistrationsController < Devise::RegistrationsController
private
def sign_up_params
params.require(:user).permit(:first_name, :last_name, :email, :password,
:password_confirmation)
end
def account_update_params
params.require(:user).permit(:first_name, :last_name, :email, :password,
:password_confirmation, :current_password)
end
end