momo: don't use cached value if it's empty

combo/apps/momo/views.py

@@ -82,7 +82,7 @@ def get_page_dict(request, page, manifest):
         page_dict['external'] = True
         page_dict['url'] = page.redirect_url
 
-    if hasattr(page, '_children'):
+    if hasattr(page, '_children') and page._children:
         children = page._children
     else:
         children = page.get_children()