When loading two different cfg one after another MMShuttersWidget gives an error

[fdrgsp]

opened from #250.

Loading two different cfg one after another will result in a error in the MMShuttersWidget (e.g. the demo config followed by real scope config).

This issue (that does not prevent the correct loading of the cfg) is here in the MMShuttersWidget

napari-micromanager/src/napari_micromanager/_gui_objects/_shutters_widget.py

Lines 29 to 37 in 60f13ca

	if not self._mmc.getLoadedDevicesOfType(DeviceType.ShutterDevice):
	# FIXME:
	# ShuttersWidget has not been tested with an empty device label...
	# it raises all sorts of errors.
	# if we want to have a "placeholder" widget, it needs more testing.
	# empty_shutter = ShuttersWidget("")
	# self.layout().addWidget(empty_shutter)
	return