fix: messages are None when no message is received

ref: N25B-265

src/control_backend/agents/bdi/behaviours/belief_setter.py

@@ -17,7 +17,9 @@ class BeliefSetterBehaviour(CyclicBehaviour):
 
     async def run(self):
         """Polls for messages and processes them."""
-        msg = await self.receive()
+        msg = await self.receive(timeout=1)
+        if not msg:
+            return
         self.agent.logger.debug(
             "Received message from %s with thread '%s' and body: %s",
             msg.sender,