app: display standard error page when no cookies are present

This occurs mostly when Safari attempts to perform a POST request
again (without sending any of the cookies).

In that case, our custom `422.html` page is more helpful to the user
(because it has a link to the previous page) than a "No cookies" blank
text.

app/controllers/application_controller/error_handling.rb

@@ -3,20 +3,21 @@ module ApplicationController::ErrorHandling
 
   included do
     rescue_from ActionController::InvalidAuthenticityToken do
-      if cookies.count == 0
-        # When some browsers (like Safari) re-open a previously closed tab, they attempts
-        # to reload the page – even if it is a POST request. But in that case, they don’t
-        # sends any of the cookies.
-        #
-        # Ignore this error.
-        render plain: "Les cookies doivent être activés pour utiliser #{APPLICATION_NAME}.", status: 403
-      else
+      # When some browsers (like Safari) re-open a previously closed tab, they attempts
+      # to reload the page – even if it is a POST request. But in that case, they don’t
+      # sends any of the cookies.
+      #
+      # In that case, don’t report this error.
+      if request.cookies.count > 0
         log_invalid_authenticity_token_error
-        raise # propagate the exception up, to render the default exception page
       end
+
+      raise # propagate the exception up, to render the default exception page
     end
   end
 
+  private
+
   def log_invalid_authenticity_token_error
     Sentry.with_scope do |temp_scope|
       tags = {

spec/controllers/application_controller/error_handling_spec.rb

@@ -33,15 +33,10 @@ RSpec.describe ApplicationController::ErrorHandling, type: :controller do
         {}
       end
 
-      it 'returns a message' do
-        post :invalid_authenticity_token
-
-        expect(response).to have_http_status(403)
-        expect(response.body).to include('cookies')
-      end
-
-      it 'renders the standard exception page' do
-        expect { post :invalid_authenticity_token }.not_to raise_error
+      it 'doesn’t log the error' do
+        allow(Sentry).to receive(:capture_message)
+        post :invalid_authenticity_token rescue nil
+        expect(Sentry).not_to have_received(:capture_message)
       end
     end
   end