title: Node-red not detecting null value
body: <p>I am trying to build a flow, that reads sensor data and transfers by CANBUS. Sometimes, <code>null</code> data is coming what I mean is <code>tempInt</code> or <code>ldrInt</code> could be null. </p>
  
  <pre><code>   var msg2 = {
     payload:
         {
             "$class": "org.acme.testnetwork.UpdateSensorData",
             "sampDevice": "houseMehmet",
             "newTempVal": tempInt,
             "newLightVal": ldrInt,
             "timeStamp": Date().toString()
         }
     };
  </code></pre>
  
  <p>Although I can access <code>msg.payload.newLightVal</code> and set it to any value, in the case that its value is null, the control statement such below fails.</p>
  
  <pre><code>if(msg.payload.newLightVal===null){
      msg.payload.newLightVal = -1 ;
  }
  </code></pre>