Check if n is populated before making a comparison

src/khoj/routers/api_chat.py

@@ -110,6 +110,7 @@ def chat_history(
         }
     )
 
+    if n:
         # Get latest N messages if N > 0
         if n > 0 and meta_log.get("chat"):
             meta_log["chat"] = meta_log["chat"][-n:]