cli: do not die on missing description

The DPI setting has no description, do not try to display it.

lib/solaar/cli/config.py

@@ -27,6 +27,7 @@ from logitech_receiver import settings as _settings
 def _print_setting(s, verbose=True):
 	print ('#', s.label)
 	if verbose:
+		if s.description:
 			print ('#', s.description.replace('\n', ' '))
 		if s.kind == _settings.KIND.toggle:
 			print ('#   possible values: on/true/t/yes/y/1 or off/false/f/no/n/0')