Instantly asks for sign in

After installation hackmd extension asks for sign in into hackmd.io account, despite the fact I was already signed in. But ok, I signed out, then pushed 'sign in' button in Firefox extension, after which I was redirected to hackmd.io site, signed in there.
And extension still asks me to sign in and redirects to the hackmd.io site where I signed in already.

FF 68.01
Ubuntu 18.04

Reproduce the sign-in flow in the Firefox extension using the reported Firefox 68.01 and Ubuntu 18.04 environment, then compare the extension's state with the already-authenticated hackmd.io session. Done means an existing signed-in account is recognized and the extension no longer repeatedly redirects to the sign-in page.

索引モデルが issue の本文から書いたものです。