Default user picture token

Problem/Motivation

Author's picture : [message:author:user_picture]

If user has not added a picture, the picture assigned by the system as default image should be visible. However, [message:author:user_picture] cannot get 'default image' of user_picture field. The default image is either not visible or shows a broken image.
The token only works if user manually add an image.

I tried to access it with a twig template, but since {{ message.author....... }} did not work either, I could not access the picture.

Any idea, please.... Thanks