Zend_Locale_Format::isNumber does not call checkOptions and validate $options['locale'] exists

    public static function isNumber($input, array $options = array())
    {
        // Get correct signs for this locale
        $symbols = Zend_Locale_Data::getList($options['locale'],'symbols');

        // Parse input locale aware
        $regex = '/^([' . $symbols['minus'] . '-]){0,1}(\d+(\\' . $symbols['group']
            . '){0,1})*(\\' . $symbols['decimal'] . '){0,1}\d+$/';
        preg_match($regex, $input, $found);

        if (!isset($found[0]))
            return false;
        return true;
    }

This can cause a php error.