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 tmortagne:

getUserReference() return null for guest on purpose, there has even been a vote for this. The old behavior of using some crappy string "XWikiGuest" is wrong and the plan is to change that while we are changing the APIs to use DocumentReference.