ExifInterface: fix creating pointer tags which indicate 0 offset

When saving attributes(that it writes JPEG again.), now ExifInterface
generates some uncessary pointer tags which refer to an empty EXIF IFD
group, that makes a warning message by ExifInterface when reading again,
which warns that the value of the pointer tag pointing to is invalid.

Bug: 27583378
Change-Id: Id0170c5644541565c98fe4978284098e6664c395