IndexError: list index out of range - get_files_completion

[sentry-for-tribler]

Sentry Issue: TRIBLER-TE

IndexError: list index out of range
  File "tribler\core\components\restapi\rest\rest_manager.py", line 50, in error_middleware
  File "aiohttp\web_middlewares.py", line 117, in impl
  File "tribler\core\components\libtorrent\restapi\downloads_endpoint.py", line 351, in get_downloads
  File "tribler\core\components\libtorrent\restapi\downloads_endpoint.py", line 155, in get_files_info_json
  File "tribler\core\components\libtorrent\download_manager\download_state.py", line 172, in get_files_completion

[xoriole]

tribler/src/tribler/core/components/libtorrent/download_manager/download_state.py

Lines 168 to 173 in a3c65eb

	if self.lt_status and self.download.handle and self.download.handle.is_valid():
	files = self.download.get_def().get_files_with_length()
	progress = self.download.handle.file_progress(flags=1)
	for index, (path, size) in enumerate(files):
	completion_frac = (float(progress[index]) / size) if size > 0 else 1
	completion.append((path, completion_frac))

Seems handle.file_progress(flags=1) can return empty list [] even though there are files present in the torrent.