Fix issue : don't delete DatasetProcessRule, DatasetQuery and AppDatasetJoin when delete dataset with no document (#3354)

api/tasks/clean_dataset_task.py

@@ -46,8 +46,8 @@ def clean_dataset_task(dataset_id: str, tenant_id: str, indexing_technique: str,
 
         if documents is None or len(documents) == 0:
             logging.info(click.style('No documents found for dataset: {}'.format(dataset_id), fg='green'))
-            return
-
+        else:
+            logging.info(click.style('Cleaning documents for dataset: {}'.format(dataset_id), fg='green'))
             index_processor = IndexProcessorFactory(doc_form).init_index_processor()
             index_processor.clean(dataset, None)