Description:
------------
In case of failure, several ODBC functions, e.g. odbc_tables() and
odbc_columns(), fail to fetch the error message.  The problem is
that odbc_sql_error() is called with SQL_NULL_HSTMT, although the
respective statement caused the error, and has appropriate error
information.

This can nicely be confirmed with the Microsoft Access Driver
(*.mdb, *.accdb), because that driver has rather limited
capabilities.


Test script:
---------------
<?php
$conn = odbc_connect($dsn, $user, $pass);
var_dump($result = odbc_tables($conn, '', '', '', ''));
var_dump(odbc_error($conn));
?>


Expected result:
----------------
Warning: odbc_tables(): SQL error: [Microsoft][ODBC-Treiber fr Microsoft Access]Optionales Feature wurde nicht implementiert. , SQL state S1C00 in SQLTables in %s on line %d
bool(false)
string(5) "S1C00"


Actual result:
--------------
Warning: odbc_tables(): SQL error: Failed to fetch error message, SQL state HY000 in SQLTables in %s on line %d
bool(false)
string(5) "HY000"