crash if no cd in drive when using this log plugin

[Hawke]

Traceback (most recent call last):
File "/usr/lib/python3/dist-packages/whipper/extern/task/task.py", line 518, in c
callable_task(*args, **kwargs)
File "/usr/lib/python3/dist-packages/whipper/program/cdrdao.py", line 111, in _read
self._done()
File "/usr/lib/python3/dist-packages/whipper/program/cdrdao.py", line 149, in _done
self.toc.parse()
File "/usr/lib/python3/dist-packages/whipper/image/toc.py", line 191, in parse
with open(self._path) as f:
FileNotFoundError: [Errno 2] No such file or directory: '/tmp/tmpirqgnyeg.cdrdao.read-toc.whipper.task'
CRITICAL:whipper.command.main:exception FileNotFoundError at /usr/lib/python3/dist-packages/whipper/image/toc.py:191: parse(): [Errno 2] No such file or directory: '/tmp/tmpirqgnyeg.cdrdao.read-toc.whipper.task'
Traceback (most recent call last):
File "/usr/lib/python3/dist-packages/whipper/extern/task/task.py", line 518, in c
callable_task(*args, **kwargs)
File "/usr/lib/python3/dist-packages/whipper/program/cdrdao.py", line 111, in _read
self._done()
File "/usr/lib/python3/dist-packages/whipper/program/cdrdao.py", line 149, in _done
self.toc.parse()
File "/usr/lib/python3/dist-packages/whipper/image/toc.py", line 191, in parse
with open(self._path) as f:
FileNotFoundError: [Errno 2] No such file or directory: '/tmp/tmpirqgnyeg.cdrdao.read-toc.whipper.task'