MqttPahoMessageHandler throwing exception [Assertion failed] - this expression must be true

Question

standalone.xml (used to test through java main class)

<bean id="clientFactory"
            class="org.springframework.integration.mqtt.core.DefaultMqttPahoClientFactory">
        <property name="userName" value="admin"/>
        <property name="password" value="admin"/>
    </bean>

    <!-- This is channel declaration -->
    <int:channel id="mqttOutChannel"/>

    <!--   This will publish the message to the specific topic -->
    <int-mqtt:outbound-channel-adapter id="mqOutAdpter"
        client-id="client1" 
        url="tcp://localhost:1883" 
        client-factory="clientFactory" 
        default-topic="testPublishMqttServer" 
        channel="mqttOutChannel" 
        auto-startup="true"
        converter="converter"/>

         <bean id="converter" class="org.springframework.integration.mqtt.support.DefaultPahoMessageConverter">

         </bean>    

        <int:inbound-channel-adapter channel="mqttOutChannel" expression="'Hi'">
            <int:poller fixed-delay="1000"></int:poller>
        </int:inbound-channel-adapter>

Java Main Class

ApplicationContext ac = new ClassPathXmlApplicationContext("/standalone.xml.xml");

MessageChannel msg = (MessageChannel)ac.getBean("mqttOutChannel");
msg.send(MessageBuilder.withPayload("My Msg").setHeader("HeaderVar", "Hello").build());
System.out.println("Its Working");

Configured XML - mqtt-outbound-context

<bean id="clientFactory"
        class="org.springframework.integration.mqtt.core.DefaultMqttPahoClientFactory">
    <property name="userName" value="${mqtt.outbound.userName}"/>
    <property name="password" value="${mqtt.outbound.passWord}"/>
</bean>

<!-- This is channel declaration -->
<int:channel id="mqttOutChannel"/>

<!--   This will publish the message to the specific topic -->
<int-mqtt:outbound-channel-adapter id="${mqtt.outbound.beanId}"
    client-id="${mqtt.outbound.clientId}" 
    url="${mqtt.outbound.brokerUrl}" 
    client-factory="clientFactory" 
    default-topic="${mqtt.outbound.topic}" 
    channel="mqttOutChannel" 
    auto-startup="true"
    converter="converter"/>


     <bean id="converter" class="org.springframework.integration.mqtt.support.DefaultPahoMessageConverter">

     </bean>    

**Code to initialize the channel - ** getOutboundMqtt is the method being invoked

public MessageChannel getOutboundMqtt(String endPoint,String brokerUrl,String topics,String userName,
            String passWord,String sourceId) {
        MessageChannel channel = myChannelDetails.getChannel("MQ_OUTBOUND", endPoint);
        if (channel == null) {
            channel = createNewChannel(endPoint, brokerUrl, topics, userName, passWord,sourceId);
        }
        return channel;
    }

    private synchronized MessageChannel createNewChannel(String endPoint,String brokerUrl,String topics,String userName,
            String passWord,String sourceId) {

            ConfigurableApplicationContext ctx = new ClassPathXmlApplicationContext(
                    new String[] { "/META-INF/spring/integration/mqtt/mqtt-outbound-context.xml" },
                    false);
            this.setEnvironmentForMqtt(ctx, endPoint, brokerUrl, topics, userName, passWord);
            ctx.refresh();
            MessageChannel channel = ctx.getBean("mqttOutChannel", MessageChannel.class);
            myChannelDetails.putChannel("MQ_OUTBOUND", endPoint, channel);

        return channel;
    }

    private void setEnvironmentForMqtt(ConfigurableApplicationContext ctx, String endPoint,String brokerUrl,String topics,String userName,
            String passWord) {
        StandardEnvironment env = new StandardEnvironment();
        Properties props = new Properties();
        props.setProperty("mqtt.outbound.brokerUrl", brokerUrl);
        props.setProperty("mqtt.outbound.topic", topics);
        props.setProperty("mqtt.outbound.userName", userName);
        props.setProperty("mqtt.outbound.passWord", passWord);
        props.setProperty("mqtt.outbound.clientId", endPoint);
        props.setProperty("mqtt.outbound.beanId", endPoint+"ID");

        PropertiesPropertySource pps = new PropertiesPropertySource("mqttProps", props);
        env.getPropertySources().addLast(pps);
        ctx.setEnvironment(env);
    }

Sending message to outbound MQTT - here is what I am facing issue

public String putMessageToChannel( String mqttChannelName,String endPoint, String msg)
             {
         myChannelDetails.getChannel(mqttChannelName,
                endPoint).send(MessageBuilder.withPayload(msg).setHeader("HeaderVar", "Hello").build());
        return  "Successfully sent the message to the recipient";
    }

Error which is getting thrown @ putMessageToChannel

org.springframework.messaging.MessageHandlingException: error occurred in message handler [org.springframework.integration.mqtt.outbound.MqttPahoMessageHandler#0]; nested exception is java.lang.IllegalArgumentException: [Assertion failed] - this expression must be true