return empty email if not current user

app/controllers/patrons_controller.rb

@@ -5,7 +5,7 @@ module DiscoursePatrons
     skip_before_action :verify_authenticity_token, only: [:create]
 
     def index
-      result = {}
+      result = { email: '' }
 
       if current_user
         result[:email] = current_user.email

spec/controllers/discourse_patrons/patrons_controller_spec.rb

@@ -23,7 +23,7 @@ module DiscoursePatrons
 
       it 'has no current user email' do
         get :index, format: :json
-        expect(JSON.parse(response.body)['email']).to be_nil
+        expect(JSON.parse(response.body)['email']).to be_empty
       end
     end