Fixes crash on iOS 8.1. Based on @neonichu's commit https://github.com/neonichu/DZNWebViewController/commit/94e7db3d6feb9db76f1f334a461110d00249a66d
Fixes crash on iOS 8.1. Based on @neonichu's commit https://github.com/neonichu/DZNWebViewController/commit/94e7db3d6feb9db76f1f334a461110d00249a66d

macoscope/DZNWebViewController,imjerrybao/DZNWebViewController,dzenbot/DZNWebViewController,iorikingdom/DZNWebViewController,RobotsAndPencils/DZNWebViewController,imjerrybao/DZNWebViewController,imjerrybao/DZNWebViewController,imjerrybao/DZNWebViewController,imjerrybao/DZNWebViewController