Backoffice is undefined certainely

I am developing with umbraco locally and the front-end site loads fine, but when I try to load the /umbraco I get nothing and no error.

It redirects to http://localhost:51989/umbraco#/undefined and there is no content, just blank.

i have fresh installed umbraco, everything was working very fine. but i unfortunately clicked to allow the sections in users/groups/administrator

after that backoffice is showing nothing. front end is working as it is. anyone has any solution … how i could get back my all pages and my project. much wired


This is a companion discussion topic for the original entry at https://our.umbraco.com/forum/103905-backoffice-is-undefined-certainely