added error handling

agent.py

@@ -190,12 +190,22 @@ def build_graph(provider: str = "google"):
 
     def retriever(state: MessagesState):
         query = state["messages"][-1].content
-        similar_doc = vector_store.similarity_search(query, k=1)[0]
+        similar_docs = vector_store.similarity_search(query, k=1)
 
+        if not similar_docs:
+            # If no similar documents are found, return a default message.
+            # This prevents the "list index out of range" error.
+            answer = "I could not find a similar question in my knowledge base."
+            return {"messages": [AIMessage(content=answer)]}
+
+        # If we found documents, proceed as before.
+        similar_doc = similar_docs[0]
         content = similar_doc.page_content
+        
         if "Final answer :" in content:
             answer = content.split("Final answer :")[-1].strip()
         else:
+            # Fallback if the document format is unexpected
             answer = content.strip()
 
         return {"messages": [AIMessage(content=answer)]}