Improve user flow for non-logged-in users attempting to create subscriptions

[calvo215]

If the user has not logged in and clicks on "subscribe to alerts," the pop-up appears, letting her choose her combination of interests for the subscription, but then when she clicks "create," there is a "failed to create subscription." I would advise that if the user hasn't logged in, when she clicks on "subscribe to alerts", we prompt her to the register/login page (?)