Get names from multinode treepicker

Questions
1

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:

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. :')

This is a companion discussion topic for the original entry at https://our.umbraco.com/forum/74409-get-names-from-multinode-treepicker