Just fixed this error. I added the 'mqm' user I was using on the docker container to my createQueueConnection call like this:
createQueueConnection
MQQueueConnection queueConn = (MQQueueConnection) cf.createQueueConnection("admin1", "");
this is the typical error when the MQ client does not provide conn creds, it can also happen in the WebSphere log when you forgot to specify creds in the Integrated Console