Moved withdrawn_event check to helper

Signed-off-by: Carlos Coelho <carlos@pencillabs.com>

app/controllers/admin/conference_controller.rb

@@ -160,9 +160,6 @@ module Admin
       # get campaigns
       @campaigns = @conference.get_campaigns
 
-      # get withdrawn events
-      @withdrawn_events = @conference.program.events.where(state: :withdrawn)
-
       respond_to do |format|
         format.html
         format.json { render json: @conference.to_json }