paho compatibility fix, skip TLS if not set

knx2mqtt

@@ -146,7 +146,7 @@ async def on_telegram_received(telegram):
         eprint(traceback.format_exc())
 
 
-def on_mqtt_connect(client, userdata, flags, rc):
+def on_mqtt_connect(client, userdata, flags, reason_code, properties):
     global daemon_args
 
     for address in daemon_args.mqtt_subscribe:
@@ -178,7 +178,8 @@ def start_mqtt():
     mqtt_client = mqtt.Client(mqtt.CallbackAPIVersion.VERSION2)
     cert_reqs = verify_mode[daemon_args.mqtt_verify_mode] if daemon_args.mqtt_verify_mode in verify_mode else None
     tls_version = tls_versions[daemon_args.mqtt_tls_version] if daemon_args.mqtt_tls_version in tls_versions else None
-    mqtt_client.tls_set(cert_reqs=cert_reqs, tls_version=tls_version)
+    if cert_reqs is not None and tls_version is not None:
+        mqtt_client.tls_set(cert_reqs=cert_reqs, tls_version=tls_version)
     if daemon_args.verbose:
         logging.basicConfig(level=logging.DEBUG)
         mqtt_client.enable_logger()