It is a warning. The warning is there to let you know that this might affect rich result appearance. It would prevent Google from linking to the author's profile in a search result, because there is no profile to link to.
I really want to be clear that Google Search Console messages are largely informational. They are there to let you know of potential problems. Some of the warnings issued are for things which are entirely deliberate, in which case there is no reasonable action to take other than ignoring them.