It is possible to send empty events via UDP

[timrourke]

https://github.com/DataDog/php-datadogstatsd/pull/70/files#diff-9370933975e4185eb4190af53b5b95deR655

The above link to my PR to add tests indicates that it is possible to send empty event data via UDP. Once test coverage is in place, I recommend DogStatsd::eventUdp be updated to return early if there isn't any data to send.