fix: Fix None error

Author: marcelklehr

ex_app/lib/agent.py

@@ -86,7 +86,7 @@ async def call_model(
 		if tool_enabled("find_details_of_current_user"):
 			system_prompt_text += "Use the find_details_of_current_user tool to find the current user's location.\n"
 
-		if task['input']['memories']:
+		if task['input'].get('memories', None) is not None:
 			system_prompt_text += "You can remember things from other conversations with the user. If relevant, take into account the following memories:\n\n" + "\n".join(task['input']['memories']) + "\n\n"
 		# this is similar to customizing the create_react_agent with state_modifier, but is a lot more flexible
 		system_prompt = SystemMessage(