Login message visible for events without registration

One-sentence description

A message and button are shown to log in to register for an event even when it is not possible to register for the event

Current behaviour / Reproducing the bug

1. Visit the Thalia website without logging in
2. Find an event for which you cannot register (e.g. a borrel)
3. You see "You have to log in before you can register for this event." and a login button

Expected behaviour

1. Visit the Thalia website without logging in
2. Find an event for which you cannot register (e.g. a borrel)
3. You do not see a message and button to log in to register