problem with $form['#validate']

sometimes I get the following error related to forms with captcha field:
" Fatal error: Unsupported operand types in ...../modules/contrib/captcha/captcha.module on line 197"

line 197 is: "$form['#validate'] += array('captcha_validate' => array());"

I guess the '+=' does not work if '$form['#validate']' is not set.

Changing that line to the following helps:
"""
if(isset($form['#validate'])) {
$form['#validate'] += array('captcha_validate' => array());
} else {
$form['#validate'] = array('captcha_validate' => array());
}
"""