Update document_stores/elasticsearch/src/elasticsearch_haystack/docum…

…ent_store.py

Co-authored-by: Silvano Cerza <[email protected]>

document_stores/elasticsearch/src/elasticsearch_haystack/document_store.py

@@ -123,7 +123,7 @@ def _search_documents(self, **kwargs) -> List[Document]:
             documents.extend(self._deserialize_document(hit) for hit in res["hits"]["hits"])
             from_ += len(documents)
 
-            if top_k and from_ >= top_k:
+            if top_k is not None and from_ >= top_k:
                 break
             if from_ >= res["hits"]["total"]["value"]:
                 break