Service Bridge transforms for state - how to do nothing for x state?

[SNAdmin47]

We are using service bridge RTD (Remote Task Definition) and have configured a state mapping transform. However, we have a state on our provider instance which when selected we do not want that state to send any state change to the consumer. Any idea how we would do that?

As a direct example, when our state changes to 'Customer Updated' (state value of 19 below) we do not want the state to be sent to the consumer. I've tried using '' or 'null' but this then results in sending a blank state which then causes issues on both instances. How can I add an 'abort' message into the transform?

if (direction == "outbound") {
    if (check == 1) {
        output.value = '1';
        output.label = 'Open';
    } else if (check == 2) {
        output.value = '2';
        output.label = 'Work in Progress';
    } else if (check == 3) {
        output.value = '-5';
        output.label = 'Pending';
    } else if (check == 7) {
        output.value = '3';
        output.label = 'Closed Complete';
    } else if (check == 8) {
        output.value = '4';
        output.label = 'Closed Incomplete';
    } else if (check == 19) {
        output.value = 'null';
        output.label = 'null';
    } else {
        output.value = '2';
        output.label = 'Work in Progress';
    }
}