Update src/rag_engine.py

src/rag_engine.py

@@ -131,6 +131,8 @@ def search_knowledge_base(query, username, k=10, final_k=4):
         # Extract just the text for the cross-encoder
         candidate_docs = [doc for doc, _ in results]
         candidate_texts = [doc.page_content for doc in candidate_docs]
+        if not candidate_texts:
+            return []
         
         # Form pairs: (Query, Document Text)
         pairs = [[query, text] for text in candidate_texts]