Fix renaming world video file if no file was written

[papr]

Follow up PR for #2167

• Fixes crash below
• Demotes "No world video recorded" log message from error to warning

Crash if no world camera is connected during recording:

world - [ERROR] launchables.world: Process Capture crashed with trace
Traceback (most recent call last):
  File ".../pupil/pupil_src/launchables/world.py", line 741, in world
    p.on_notify(n)
  File ".../pupil/pupil_src/shared_modules/recorder.py", line 289, in on_notify
    self.stop()
  File ".../pupil/pupil_src/shared_modules/recorder.py", line 497, in stop
    self.writer.release()
  File ".../pupil/pupil_src/shared_modules/av_writer.py", line 243, in release
    self.close()
  File ".../pupil/pupil_src/shared_modules/av_writer.py", line 234, in close
    os.rename(self.output_file_path_in_porgress, output_file_path)
FileNotFoundError: [Errno 2] No such file or directory: '.../recordings/2021_09_08/000/world.mp4.writing' -> '.../recordings/2021_09_08/000/world.mp4'