bitcoinj/bitcoinj — pull request #259 by devrandom (2014-10-30 18:08:42+00:00)
Title: Don't allow creation of seeds with null passphrase

It should be the empty string as the standard default. Right now if people use the builder pattern, they get the string "null" in the passphrase. Since this is a new API as of 0.12, I'm assuming that nobody ran into this yet.