A log without a message is not allowed by some log services

[hdumazeau]

| Symfony version | 5.4.x | Bundle version | 8.3.0

Some log services no longer allow logging without a message. For example the graylog2/gelf-php bundle required by monolog/monolog does not allow this in the latest version: https://github.com/bzikarsky/gelf-php/blob/master/src/Gelf/MessageValidator.php#L53

In your bundle, a log without message exists: https://github.com/8p/EightPointsGuzzleBundle/blob/master/src/Middleware/LogMiddleware.php#L44