Tag from exiftool on MP4 not visible on 0.28

[Massimo-B]

Describe the bug

As described in BestImageViewer/geeqie#1034 (comment) we found a regression in 0.28 compared to 0.27.

To Reproduce

Steps to reproduce the behavior:
I have set a tag like this:

exiftool -Artist="Mo" -overwrite_original_in_place -preserve VID_20240526_112118.mp4

Looking at the file with exiv2 0.28, the flag isn't there:
exiv2 -p x VID_20240526_112118.mp4

Desktop (please complete the following information):

• OS and version: Gentoo Linux
• Exiv2 version and source: 0.28
• Compiler and version: gcc x86_64-pc-linux-gnu-13