Fixed attaching lock failure

        else:

            self.rc = OpenflexureConfig(expand=True)  # Load config from default path

        # Initialise with an empty composite lock

        self.lock = CompositeLock([])  #: :py:class:`openflexure_microscope.lock.CompositeLock`: Composite lock controlling thread access to multiple pieces of hardware

        # Attach initial hardware (may be NoneTypes)

        self.camera = None

        self.stage = None

        if 'fov' not in self.rc.config:

            self.rc.write({'fov': [0, 0]})

        # Initialise with an empty composite lock

        self.lock = CompositeLock([])  #: :py:class:`openflexure_microscope.lock.CompositeLock`: Composite lock controlling thread access to multiple pieces of hardware

    def __enter__(self):

        """Create microscope on context enter."""