message: fix condition not to behave erratic in case of custom handler for Curl.option.HEADERFUNCTION
diff: @@ -970,7 +970,7 @@ Curl.prototype.setOpt = function(optionIdOrName, optionValue) {
  // since if they are set back to null, we must restore the default callback.
  if ((optionIdOrName === Curl.option.WRITEFUNCTION || optionIdOrName === 'WRITEFUNCTION') && !optionValue) {
  optionValue = this._onData.bind(this);
  - } else if (optionIdOrName === Curl.option.HEADERFUNCTION || (optionIdOrName === 'HEADERFUNCTION' && !optionValue)) {
  + } else if ((optionIdOrName === Curl.option.HEADERFUNCTION || optionIdOrName === 'HEADERFUNCTION') && !optionValue) {
  optionValue = this._onHeader.bind(this);
  }
  