xwiki/xwiki-platform — comment on commit 7fe467a89c3152ed25ec23476d77a1b4a8589f9d
File: xwiki-platform-core/xwiki-platform-oldcore/src/main/java/com/xpn/xwiki/api/Document.java line 2018
By vmassol:

Are you sure about this?

I'm asking because the code you've changed was doing doc.setAuthor() and the code for setAuthor(String) is:

public void setAuthor(String author)
{
// Note: Consider "" or null as the same, i.e. the author not being set
DocumentReference authorReference = null;
if (author != null && author.length() > 0) {
authorReference =
this.explicitReferenceDocumentReferenceResolver.resolve(
this.xClassEntityReferenceResolver.resolve(author, EntityType.DOCUMENT), getDocumentReference());
}

if ((getAuthorReference() == null && authorReference != null)
|| (getAuthorReference() != null && !getAuthorReference().equals(authorReference))) {
setMetaDataDirty(true);
}

setAuthorReference(authorReference);
}

I don't see the setting to XWikiGuest when the passed author string is null in there so this would mean you've changed the current behavior.