Fixed crash when trying to rotate image when bitmap == null.
Fixed crash when trying to rotate image when bitmap == null.

qingsong-xu/cropper,nbumakov/Android-Image-Cropper,xiaalngf/cropper,hanumanthan/cropper,Owenhwy/cropper,chengkaizone/cropper,huy510cnt/Cropper-Image,ArthurHub/Android-Image-Cropper,anotherdev/cropper,mumer92/Android-Image-Cropper,samkirton/cropper,msdx/cropper,lczgywzyy/cropper,msdgwzhy6/cropper,ileisure/cropper,fhchina/cropper,hgl888/cropper,tibbi/Android-Image-Cropper,ArthurHub/Android-Image-Cropper,boojtran/cropper,peterdocter/cropper,chwnFlyPig/cropper,gtbX/cropper,akhilesh0707/Android-Image-Cropper,tibbi/Android-Image-Cropper,voltazor/cropper,jjfreeze/Android-Image-Cropper,murat8505/Android-Image-Cropper,jaohoang/cropper,binzzeng/cropper,jinshiyi11/cropper,timothylcooke/Android-Image-Cropper,wyxacc/cropper,Sshah88/cropper,liwangdong/cropper,wuyajun7/cropper,Gangadhar82/Android-Image-Cropper,adamin1990/cropper,wlmxj/cropper,timothylcooke/Android-Image-Cropper,GMAndroidTeam/cropper,vfishv/cropper