[fw-db] bug(?!) empty configuration node strange affects

This is database section of my configuration file:
  <database>
    <connection>
      <adapter>pdo_mysql</adapter>
      <params>
        <host>192.168.1.177</host>
        <dbname>bbdo</dbname>
        <username>script</username>
        <password>script_stupid</password>
      </params>
    </connection>
  </database>

This is a MySql log file section as a result of connecting:

090331  0:29:17      92 Connect     script@192.168.1.177 on bbdo
                     92 Query       set names utf8
                     92 Query       DESCRIBE `courses`
                     92 Query       SELECT `courses`.* FROM `courses` WHERE (specialised = false)
........................

Everything good.
But.
This is slightly modified version. I simply add empty node <driver_options> (i have another problem related with and i leave it blank).
  <database>
    <connection>
      <adapter>pdo_mysql</adapter>
      <params>
        <host>192.168.1.177</host>
        <dbname>bbdo</dbname>
        <username>script</username>
        <password>script_stupid</password>
        <driver_options>
         
        </driver_options>
      </params>
    </connection>
  </database>


MySql log shows:
090331  0:33:08      93 Connect     script@192.168.1.177 on bbdo
                     93 Query       SET AUTOCOMMIT=0  /* <<<< WHAT IS THIS!? */
                     93 Query       set names utf8
                     93 Query       DESCRIBE `courses`
                     93 Query       SELECT `courses`.* FROM `courses` WHERE (specialised = false)
........................

As you see, a very strange line "SET AUTOCOMMIT=0" appears.

As result of this line, my inserts not works at all, but without any error messages, (and these inserts appears normally in mysql log).

I spend big time trying to understand why my inserts not working, and finally without any hope i try to delete unsuspicious _empy_ '<driver_options>' node from xml configuration, and it  works normally now.

But why _empty_(!) '<driver_options>' node make so effect?
It is a bug? Or what i doing wrong?

Thanks!