var submessage = (function () {

var exports = {};

exports.get_message_events = function (message) {
    if (message.locally_echoed) {
        return;
    }

    if (!message.submessages) {
        return;
    }

    if (message.submessages.length === 0) {
        return;
    }

    message.submessages.sort(function (m1, m2) {
        return parseInt(m1.id, 10) - parseInt(m2.id, 10);
    });

    var events = _.map(message.submessages, function (obj) {
        return {
            sender_id: obj.sender_id,
            data: JSON.parse(obj.content),
        };
    });

    return events;
};

exports.process_submessages = function (in_opts) {
    var message_id = in_opts.message_id;
    var message = message_store.get(message_id);

    if (!message) {
        return;
    }

    var events = exports.get_message_events(message);

    if (!events) {
        return;
    }

    var row = in_opts.row;

    // Right now, our only use of submessages is widgets.

    var data = events[0].data;

    if (data === undefined) {
        return;
    }

    var widget_type = data.widget_type;

    if (widget_type === undefined) {
        return;
    }

    var post_to_server = exports.make_server_callback(message_id);

    widgetize.activate({
        widget_type: widget_type,
        extra_data: data.extra_data,
        events: events,
        row: row,
        message: message,
        post_to_server: post_to_server,
    });
};


exports.handle_event = function (event) {
    blueslip.info('handle submessage: ' + JSON.stringify(event));

    // Right now, our only use of submessages is widgets.
    var msg_type = event.msg_type;

    if (msg_type !== 'widget') {
        blueslip.warn('unknown msg_type: ' + msg_type);
        return;
    }

    widgetize.handle_event({
        sender_id: event.sender_id,
        message_id: event.message_id,
        data: event.data,
    });
};

exports.make_server_callback = function (message_id) {
    return function (opts) {
        var url = '/json/submessage';

        channel.post({
            url: url,
            data: {
                message_id: message_id,
                msg_type: opts.msg_type,
                content: JSON.stringify(opts.data),
            },
        });
    };
};

return exports;

}());
if (typeof module !== 'undefined') {
    module.exports = submessage;
}

@@ -639,24 +639,364 @@
 (in_opts) %7B%0A
+    // This happens in our rendering path, so we try to limit any%0A    // damage that may be triggered by one rogue message.%0A    try %7B%0A        return exports.do_process_submessages(in_opts);%0A    %7D catch (err) %7B%0A        blueslip.error('in process_submessages: ' + err.message);%0A    %7D%0A%7D;%0A%0Aexports.do_process_submessages = function (in_opts) %7B%0A
     var mess

Add try/catch around main entry point.