[commands] Fix config command to accept zero arguments

src/hci/commands/config_cmd.c

 	}
 
 	settings_name = ( ( argc == 2 ) ? argv[1] : "" );
-	settings = find_settings ( argv[1] );
+	settings = find_settings ( settings_name );
 	if ( ! settings ) {
 		printf ( "No such scope \"%s\"\n", settings_name );
 		return 1;