Stop fetching if the user hasn't logged in

[uier]

The script loads and runs on entering hackmd.io website.

Currently, no matter the user is logged in or not, the fetches run and try to get users' notes data, which needs authentication, to provide the service. And if the user has NOT logged in, the fetches fail and 3 retries begin, and of course the retries will all fail.

Would be great if we stop at the first fetch call when we recognize that the user has not logged in.