Trigger rule on empty MQTT message?

[Samuel235]

Is anyone aware of any way at all to trigger a rule to execute if openHAB receives a blank message via MQTT?

At the moment the below code works but only if the message contained a value, i need it to trigger if the message is blank.

rule "solve"
        when
                Item monitor1 received update
        then
                V_VAR1send.postUpdate(V_VAR1.state)
end

I have a open question on the openHAB forum but wondered if anyone around here has done something similar?