Can't assign timezone default because of erroneous array_merge()

This row in domain_conf.admin.inc destroys the numeric keys of the option array:

if ($action['#form']['#type'] == 'select') {
  $action['#form']['#options'] = array_merge(array(NULL => t('Use primary domain settings')), $action['#form']['#options']);
}

This makes assigning a different timezone impossible since the key in that option array is the numeric offset in seconds for the timezones.

I'm attaching a patch for this that replaces array_merge() with a plus.

Reference: http://se2.php.net/operators.array and http://goodold.se/blog/tech/danger-id-numbers-keys-php-arrays