Woodman crashes on empty messages sent to the console

[tidoust]

Woodman does not like it when the final message it is about to send to the console is empty. This happens when:

1. the pattern makes it possible to generate an empty message as in woodman.load('console %message');
2. the call to the logging function does not provide any useful message as in logger.log(), logger.log(null) or logger.log('{}')

This should hardly ever occur in practice since it does not make a lot of sense to log nothing.