Only delete if default_headers is defined
Only delete if default_headers is defined

Otherwise it will break on Rails 3

eoy/secureheaders,wlchou/secureheaders,wlchou/secureheaders,eoy/secureheaders,codelion/secureheaders,jacobbednarz/secureheaders,davidhan527/secureheaders,reedloden/secureheaders,reedloden/secureheaders,codelion/secureheaders,twitter/secureheaders,didacte/secureheaders,eoy/secureheaders,codelion/secureheaders,didacte/secureheaders,wlchou/secureheaders,reedloden/secureheaders,didacte/secureheaders