Illustrator CC 2017 breaks on BridgeTalk script execution

The following piece of code was functioning wonderfully until illustrator CC 2017. This function is a trampoline for us to invoke scripts from an ExtendScript UI, which are passed as a string into the function.

function BTExecuteScript(jsscript){

    // create a BridgeTalk message for Illustrator to execute jssscript.

    var btMessage = new BridgeTalk;

    btMessage.target = illustrator.targetName;

    btMessage.body =  jsscript;

    btMessage.onResult = function(bto) {BridgeTalk.bringToFront(bto.sender);};

    btMessage.onError = function(errorMsgObject) { // error handler defined here

        alert("Error: "+errorMsgObject.body);

    };   

    btMessage.send();

}

Since upgrading to CC 2017, however, we get the  following error:

Any help will be much appreciated!