text: Title: Execution fails if standard streams are not available
  Body: My Python programs rely on the robot framework, and when I package and run them using a wrapper like pyinstaller, an error is reported here if the packaging parameter console is set to False
  
  robot\running\outputcapture.py 47L
  
  `    def _release_and_log(self):
          stdout, stderr = self._release()
          if stdout:
              LOGGER.log_output(stdout)
          if stderr:
              LOGGER.log_output(stderr)
              sys.__stderr__.write(console_encode(stderr, stream=sys.__stderr__))`
  
  
  The error message is
  `sys.__stderr__.write(console_encode(stderr, stream=sys.stderr))
  AttributeError: 'NoneType' object has no attribute 'write'`
  