correct error to create empty optional dict.

workflow/Snakefile

@@ -38,8 +38,8 @@ if missing:
     logger.error(err_msg)
     raise ValueError(err_msg)
 # Check if optional field available
-if 'optional' not in config or config['optional'] != dict:
-    logger.info(f'No "optional" field found or no valid configuration for config.yaml.')
+if 'optional' not in config or type(config['optional']) not in [OrderedDict, dict]:
+    logger.info(f'No "optional" field found or no valid configuration.')
     config['optional'] = {}
 # Check optional fields and include in config if not present
 for optkey, value in template_config['optional'].items():