Avoid segv when no username is passed
Note that ODBCRouter doesn't directly implement ODBC 3.0, so using it here won't really work. Expand the ODBC 3 check to better explain what happened and how to make progress (e.g.: use an ODBC manager library like unixODBC).
Tested against IBM DB2 and unixODBC. Could work with others.
Will not build under unix yet.