feat(frontend): add signout when authIdentity is nullish

[AntonioVentilii]

Motivation

As suggested by @DenysKarmazynDFINITY , we include function nullishSignOut in the check for authIdentity inside LoaderUserProfile.

[peterpeterparker]

We should probably not do this change here as it can lead to a race condition where sign out might happens twice or more?

Use click on "Logout".
Logout function reset auth identity. (it reloads the window but let's assume here for some reason the window is not reloaded)
Auth identity is null.
Subscriber start.
Auth identity is null.
Logout function call.
Logout function reset identity.
etc.

In other words, we should maybe not use nullishSignOut in an observable that uses $authIdentity because the former impacts the later?

[AntonioVentilii]

Agreed! PR closed