Prevent crash when superview is nil
Prevent crash when superview is nil

bangslosan/ImagePickerSheetController,jabez1314/ImagePickerSheetController,machelix/ImagePickerSheetController,hejunbinlan/ImagePickerSheetController,bangslosan/ImagePickerSheetController,jabez1314/ImagePickerSheetController,jiaopen/ImagePickerSheetController,acavanaghww/ImagePickerSheetController,hejunbinlan/ImagePickerSheetController,jabez1314/ImagePickerSheetController,acavanaghww/ImagePickerSheetController,jiaopen/ImagePickerSheetController,bangslosan/ImagePickerSheetController,mohsinalimat/ImagePickerSheet,larcus94/ImagePickerSheetController,mohsinalimat/ImagePickerSheet,hulu001/ImagePickerSheetController,hulu001/ImagePickerSheetController,lbrndnr/ImagePickerSheetController,colemancda/ImagePickerSheetController,machelix/ImagePickerSheetController,liangxianzhe/ImagePickerSheetController,larcus94/ImagePickerSheetController,machelix/ImagePickerSheetController,alexsanderkhitev/ImagePickerSheetController,colemancda/ImagePickerSheetController,alexsanderkhitev/ImagePickerSheetController,lbrndnr/ImagePickerSheetController,liangxianzhe/ImagePickerSheetController,colemancda/ImagePickerSheetController,mohsinalimat/ImagePickerSheet,hejunbinlan/ImagePickerSheetController