LDAP Identity Provide should correctly handle empty string

When providing an empty password string to the checkPassword method we encounter an OperationNotSupportedException. Please find attached the complete stacktrace as well as a unit test to reproduce.

When using the Microsoft LDAP implementation however an empty password string results in a positive return value. So anyone and everyone is able to login when leaving the password field in Tasklist empty.

public void testLdapLoginEmptyPassword()

{ assertFalse(identityService.checkPassword("roman", "")); }