The error message from RestApiServlet that is displayed if a user doesn't have a required capability, prints the user's username. This username may be null, as fallback now the fullname and preferred email address of the user are printed. Change-Id: I786be9d1772b76eb6712d49cebe867b20d32d975 Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>