fix crash on < iOS 7
fix crash on < iOS 7

SVProgressHUD/SVProgressHUD,Kevin775263419/SVProgressHUD,ddc391565320/SVProgressHUD,pplant/SVProgressHUD,bhapca/SVProgressHUD,CPF183/SVProgressHUD,kohtenko/SVProgressHUD,flovilmart/SVProgressHUD,powerhome/SVProgressHUD,lookingstars/SVProgressHUD,cnzlh/SVProgressHUD,zdiovo/SVProgressHUD,lyndonChen/SVProgressHUD,z514306470/SVProgressHUD,pengleelove/SVProgressHUD,maxcampolo/SVProgressHUD,wrcj12138aaa/SVProgressHUD,cogddo/SVProgressHUD,SixFiveSoftware/SVProgressHUD,apascual/SVProgressHUD,siburb/SVProgressHUD,sdonly/SVProgressHUD,RyanCodes/SVProgressHUD,cuppi/SVProgressHUD,hyperoslo/SVProgressHUD,ashfurrow/SVProgressHUD,Karumi/SVProgressHUD,1yvT0s/SVProgressHUD,dxt/SVProgressHUD,bertramdev/SVProgressHUD,hnney/SVProgressHUD,isghe/SVProgressHUD,zeptolee/SVProgressHUD,hanangellove/SVProgressHUD,TransitApp/SVProgressHUD,adrum/SVProgressHUD,Sunday4/SVProgressHUD,emodeqidao/SVProgressHUD,Dschee/SVProgressHUD,basvankuijck/SVProgressHUD,CoderJFCK/SVProgressHUD,icepy/SVProgressHUD,morgman/TASVProgressHUD,cnbin/SVProgressHUD,wjszf/SVProgressHUD,haiiev/SVProgressHUD,lzhao18/SVProgressHUD,phildow/SVProgressHUD,Staance/SVProgressHUD,ohyeslk/SVProgressHUD,ShyHornet/SVProgressHUD,ShowerLi1991/SVProgressHUD,zoyi/SVProgressHUD,shenhzou654321/SVProgressHUD,ezescaruli/SVProgressHUD,hoowang/SVProgressHUD,taviscaron/SVProgressHUD,iamcharleych/SVProgressHUD,grachyov/SVProgressHUD,Pingco/SVProgressHUD,PeeJWeeJ/SwiftyHUD,Alsen007/SVProgressHUD,pblondin/SVProgressHUD,HelloWilliam/SVProgressHUD,dongdonggaui/SVProgressHUD,shizu2014/SVProgressHUD,tonyunreal/SVProgressHUD,yarneo/SVProgressHUD,DramaFever/DFProgressHUD,PeeJWeeJ/SwiftyHUD,SuPair/SVProgressHUD,huqiji/SVProgressHUD,AutoScout24/SVProgressHUD