[Windows] Ignore FS moves with no source path

Issue

Sentry Issue: NUXEO-DRIVE-2JP

ValueError: WindowsPath('.') has an empty name
  File "nxdrive\engine\watcher\local_watcher.py", line 983, in handle_watchdog_event
  File "nxdrive\utils.py", line 523, in normalize_event_filename
  File "pathlib.py", line 826, in with_name

Logs are showing those lines before the exception (both same error):

Handling watchdog event [moved] on None to 'C:\\Users\\USER\\Documents\\folder
subsolder'

Handling watchdog event [moved] on '' to 'C:\\Users\\USER\\Documents\\folder\\subfolder1
subfolder2'

Analysis

The cause is that the FS event has first the source path on the NTFS stream (c:\folder\file.ext:nxdrive). Then it triggers more events but this time without source path.
How it happens is not yet known.