If certain characters exist in the name, display_name is set to empty string

I am adding authors using command line (wp cli) and few authors have following characters (é, ç, etc) in their name. It throws an exception. **Note that I modified some code to check what the error is**


sanitize_text_field() is returning an empty string for names with those characters.

Start by reproducing the author-creation path through WP-CLI with names containing characters such as é and ç, then inspect where sanitize_text_field() is called and where display_name becomes empty. Confirm the exception and compare behavior with names using basic characters; done means accented author names retain a non-empty display_name without throwing an exception.

Written by the indexing model from the issue text.