I have a multinode treepicker with the alias "tags". I want to get the actual names of the picks and extend them to the URL archiveLink, so that I ideally end up with something like: http://url.com/#filters=filter1,filter2,filter3

var archiveLink = Umbraco.NiceUrl(3382);

if (CurrentPage.HasValue("tags")) {
    IEnumerable<IPublishedContent> allTags = Model.Content.GetPropertyValue<IEnumerable<IPublishedContent>>("tags");

    archiveLink += "#filters=";

    foreach (var tag in allTags) {
        archiveLink += tag.Name<text>,</text>;
    }
}

I get this error: Object reference not set to an instance of an object. And I honestly have no clue what to do.. Yelp. :')