[client] Better management of empty in list

Author: Samuel Hassine

examples/export_intrusion_set_stix2.py

@@ -14,7 +14,7 @@
 intrusion_set = opencti_api_client.intrusion_set.read(filters=[{'key': 'name', 'values': ['APT28']}])
 
 # Create the bundle
-bundle = opencti_api_client.stix2.export_entity('campaign', '0d31f298-da86-4330-8c0a-4fcfa44f6ae0', 'full')
+bundle = opencti_api_client.stix2.export_entity('intrusion-set', intrusion_set['id'], 'full')
 json_bundle = json.dumps(bundle, indent=4)
 
 # Write the bundle