idevicebackup4: return success for empty DLMessageUploadFiles messages
idevicebackup4: return success for empty DLMessageUploadFiles messages

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