Occasional NullPointerException in PasswordUtil.generateSaltedHash

1. Press Sign up
2. Enter details and press the sign up button
3. Press log in
4. Enter username / password from step 2 and click Log In
5. On the "Account is not activated" page, enter a new email into the field and press Update email

Actual:
Zanata displays a success message, but on the server an exception has occurred (and no email was actually sent). Intermittently.

Expected:
No exception