respond with empty json if email does not exist

app/controllers/discourse_donations/charges_controller.rb

@@ -7,22 +7,34 @@ module DiscourseDonations
     skip_before_filter :verify_authenticity_token, only: [:create]
 
     def create
-      Stripe.api_key = SiteSetting.discourse_donations_secret_key
-      currency = SiteSetting.discourse_donations_currency
+      if email.nil?
+        response = {
 
-      customer = Stripe::Customer.create(
-       :email => params[:email] || current_user.email,
-       :source  => params[:stripeToken]
-      )
+        }
+      else
+        Stripe.api_key = SiteSetting.discourse_donations_secret_key
+        currency = SiteSetting.discourse_donations_currency
 
-      charge = Stripe::Charge.create(
-        :customer    => customer.id,
-        :amount      => params[:amount],
-        :description => SiteSetting.discourse_donations_description,
-        :currency    => currency
-      )
+        customer = Stripe::Customer.create(
+         :email => email,
+         :source  => params[:stripeToken]
+        )
 
-      render :json => charge
+        response = Stripe::Charge.create(
+          :customer    => customer.id,
+          :amount      => params[:amount],
+          :description => SiteSetting.discourse_donations_description,
+          :currency    => currency
+        )
+      end
+
+      render :json => response
+    end
+
+    private
+
+    def email
+      params[:email] || current_user.try(:email)
     end
   end
 end

spec/controllers/discourse_donations/charges_controller_spec.rb

@@ -14,6 +14,11 @@ module DiscourseDonations
       expect(response).to have_http_status(200)
     end
 
+    it 'responds ok when the email is empty' do
+      post :create, { }
+      expect(response).to have_http_status(200)
+    end
+
     it 'responds ok for logged in user' do
       current_user = log_in(:coding_horror)
       post :create