Yes it is, but goussej mentioned it was somehow wrapped in an error so that he couldn't catch it.
Anyway, since it works now, I'm guessing it was a different problem and the 'Error' was a red herring.
The error doesn't come from my game. The only class that handles the sound doesn't create such logs. You can check it by deactivating the sound, modifying my source code (remove the try/catch close in main.SoundSystem) and compile all, the default ANT target generates a JAR file, there is another target to start the game.