Set user to AnonymousUserMixin when logging out
Set user to AnonymousUserMixin when logging out

This ensures that current_user.is_authenticated will always work.
Previously, upon logout, the current_user was set to None, which would
cause calls to current_user.is_authenticated to fail.

wuvt/wuvt-site,wuvt/wuvt-site,wuvt/wuvt-site,wuvt/wuvt-site