I don't have a source and I don't quite remember where I heard it. It's probably not true. Although this post from Lambda the Ultimate mentions a similar sentiment:
It's still a bit weird, I think: a lot of the migration to Java was from enterprise C++, and while C++ has null pointers it doesn't have null references. So that wouldn't have been much of a change.
http://lambda-the-ultimate.org/node/1905#comment-23217