smol fixes

app.py

@@ -37,8 +37,8 @@ with open(TMP_DIR+"jupyter-agent.ipynb", 'w', encoding='utf-8') as f:
 
 with open("ds-system-prompt.txt", "r") as f:
     DEFAULT_SYSTEM_PROMPT = f.read()
-DEFAULT_SYSTEM_PROMPT = """You are a coding agent with access to a Jupyter Kernel.\
-The following files are available:
+DEFAULT_SYSTEM_PROMPT = """You are a coding agent with access to a Jupyter Kernel. \
+The following files are available (if any):
 {}
 """
 
@@ -75,7 +75,7 @@ def execute_jupyter_agent(
         message_history.append(
             {
                 "role": "system",
-                "content": sytem_prompt.format("- " + "\n- ".join(filenames)),
+                "content": sytem_prompt.format("- " + "\n- ".join(filenames)) if files is not None else "None",
             }
         )
     message_history.append({"role": "user", "content": user_input})