[DS-1569] Don't try to emit a password if there is none.

Issue #DS-1569 - RoleDisseminator fails to check for possible null password

dspace-api/src/main/java/org/dspace/eperson/EPerson.java

@@ -905,7 +905,7 @@ public class EPerson extends DSpaceObject
     /**
      * Return the EPerson's password hash.
      *
-     * @return hash of the password
+     * @return hash of the password, or null on failure (such as no password).
      */
     public PasswordHash getPasswordHash()
     {