update empty document caused delete exist collection (#6392)

api/tasks/document_indexing_update_task.py

@@ -46,6 +46,7 @@ def document_indexing_update_task(dataset_id: str, document_id: str):
         index_processor = IndexProcessorFactory(index_type).init_index_processor()
 
         segments = db.session.query(DocumentSegment).filter(DocumentSegment.document_id == document_id).all()
+        if segments:
             index_node_ids = [segment.index_node_id for segment in segments]
 
             # delete from vector index