"Error: Invalid action specified" from MQTT node

Hi, after upgrading from 2.0.4 to 3.0.2, I'm getting an error in Debug sidebar from an MQTT output node. This MQTT output node exists within a subflow template, which always worked before. Here's the message as it enters MQTT output, plus the error (when I click on the error's node source, it highlights MQTT node):

In case you are wondering what the incoming msg.action is about - that's just a property of the msg object that I added as part of my code. Maybe the property name "action" is conflicting with something else?

Is there any way I can revert to the previous behaviour, (without rolling back to previous version of Node-RED) as right now I can't turn my lights on :stuck_out_tongue:

(In seriousness, I do have other means of turning the lights on, just not as convenient!)

Have a look at the help text for the node. msg.action now allows you to connect and disconnect dynamically.