message: make sure that the downloads count doesn't go below 0
diff: @@ -163,6 +163,7 @@ define(["Tone/core/Tone", "Tone/core/Emitter", "Tone/type/Type"], function(Tone)
  this._buffer = null;
  if (this._xhr){
  Tone.Buffer._currentDownloads--;
  + Math.max(Tone.Buffer._currentDownloads, 0);
  this._xhr.abort();
  this._xhr = null;
  }
  