uniweb: Fix tags filter for articles

uniweb/models.py

@@ -404,7 +404,9 @@ class UniwebArticlesIndexPage(Page, SubpageMixin, MetadataPageMixin):
             articles = articles.filter(uniwebarticlepage__tags__name=tag)
 
         context["articles"] = Paginator(articles, ARTICLES_PER_PAGE).get_page(num)
-        context["tags"] = UniwebArticleTag.tags_for(UniwebArticlePage)
+        context["tags"] = UniwebArticleTag.tags_for(UniwebArticlePage).filter(
+            uniwebarticlepage__in=articles
+        )
         context["active_tag"] = tag
         return context