Avoid "notify called synchronously" when port callbacks throw

[rtfeldman]

See elm/error-message-catalog#31 for original discussion.

This code is a workaround for end users until core has a fix:

function safeSubscribe(ports, name, callback) {
    ports[name].subscribe(function(value) {
        try {
            callback(value);
        } catch(e) {
            setTimeout(function() {
                // rethrow things how you want, mention 'name' so you know who caused it
            }, 0);
        }
    });
}

Per @evancz, should be a tiny fix here.

[evancz]

notify does not exist anymore, so this cannot be a thing anymore. (I'm pretty sure!)

[evancz]

notify does not exist anymore, so this cannot be a thing anymore. (I'm pretty sure!)