Fix for behavioral bugs after changing a view controller.
Fix for behavioral bugs after changing a view controller.

SummerHF/PKRevealController,duanhjlt/PKRevealController,policp/PKRevealController,adonoho/PKRevealController,RyanTech/PKRevealController,wayne798/PKRevealController,SanChain/PKRevealController,wubangjunjava/PKRevealController,andyFang1688/PKRevealController,cnbin/PKRevealController,hanangellove/PKRevealController,libiao88/PKRevealController,AbooJan/PKRevealController,nitxc/PKRevealController,SuPair/PKRevealController,pengleelove/PKRevealController,emodeqidao/PKRevealController,chieryw/PKRevealController,pkluz/PKRevealController,ramoslin02/PKRevealController,xiaotaijun/PKRevealController,leasual/PKRevealController,xingyuniu/PKRevealController,wjszf/PKRevealController,BlessNeo/PKRevealController,adonoho/PKRevealController,AlanJN/PKRevealController,chengkaizone/PKRevealController,adonoho/PKRevealController