Improve check for BackupTotalSizeKey and improve message reporting total size
Improve check for BackupTotalSizeKey and improve message reporting total size

libimobiledevice-win32/libimobiledevice,Tatsh/libimobiledevice,libimobiledevice/libimobiledevice,libimobiledevice/libimobiledevice,libimobiledevice-win32/libimobiledevice,Tatsh/libimobiledevice,upbit/libimobiledevice,patweb/libimobiledevice,kalev/libimobiledevice,patweb/libimobiledevice,upbit/libimobiledevice,kalev/libimobiledevice,Tatsh/libimobiledevice,kalev/libimobiledevice,upbit/libimobiledevice,patweb/libimobiledevice,Tatsh/libimobiledevice,libimobiledevice-win32/libimobiledevice,libimobiledevice-win32/libimobiledevice