fix(templatetags): assumed menu item redirect_url

Do not assume a menu item has the attribute redirect_url.

This assumption caused template crash on loading news article that has category assigned.

taccsite_cms/templatetags/tacc_uri_shortcuts.py

@@ -111,7 +111,7 @@ def get_menu_uri(menu_item):
             {{ child.get_menu_title }}</a>
             # <a href="https://otherwebsite.com/some-page">some page there</a>
     """
-    if menu_item.attr['redirect_url']:
+    if hasattr(menu_item.attr, 'book_name'):
         return menu_item.attr['redirect_url']
     else:
         return menu_item.get_absolute_url()