Handle the case when title is None (#7941)

examples/rag/use_own_knowledge_dataset.py

@@ -35,8 +35,9 @@ def split_documents(documents: dict) -> dict:
     """Split documents into passages"""
     titles, texts = [], []
     for title, text in zip(documents["title"], documents["text"]):
+        if text is not None:
             for passage in split_text(text):
-            titles.append(title)
+                titles.append(title if title is not None else "")
                 texts.append(passage)
     return {"title": titles, "text": texts}