templatetags: avoid failing on nav_items when no station is defined

aircox/templatetags/aircox.py

@@ -96,6 +96,8 @@ def do_player_live_attr(context):
 @register.simple_tag(name="nav_items", takes_context=True)
 def do_nav_items(context, menu, **kwargs):
     """Render navigation items for the provided menu name."""
+    if not getattr(context["request"], "station"):
+        return []
     station, request = context["station"], context["request"]
     return [(item, item.render(request, **kwargs)) for item in station.navitem_set.filter(menu=menu)]