Handle notification_id query param gracefully for project show

There is no need to block users from viewing a project when
someone is sharing a link from his notifications with the
`notification_id` attached as a query param. The `notification_id`
query param is used to render the notification toolbar for an
authorized users. If someone without authorization is using the
same link, we should simply not render the toolbar, but still show
the project show view.

src/api/app/controllers/webui/project_controller.rb

@@ -44,11 +44,7 @@ def show
     @has_patchinfo = @project.patchinfos.exists?
     @comments = @project.comments
     @comment = Comment.new
-
-    if User.session && params[:notification_id]
-      @current_notification = Notification.find(params[:notification_id])
-      authorize @current_notification, :update?, policy_class: NotificationPolicy
-    end
+    @current_notification = handle_notification
 
     respond_to do |format|
       format.html
@@ -474,4 +470,14 @@ def set_project_by_name
   rescue Project::UnknownObjectError
     @project = nil
   end
+
+  def handle_notification
+    return unless User.session && params[:notification_id]
+
+    current_notification = Notification.find(params[:notification_id])
+
+    return unless NotificationPolicy.new(User.session, current_notification).update?
+
+    current_notification
+  end
 end