message: Include the caught exception in the thrown MslEncoderException.
diff: try {
  json = this._remainingData.concat(textEncoding.getString(data, this._charset));
  } catch (e) {
  - throw new MslEncoderException("Invalid JSON text encoding.");
  + throw new MslEncoderException("Invalid JSON text encoding.", e);
  }
  var parser = new ClarinetParser(json);
  