Notify user they are already registered for an event when looking at the event info page

A message "Oops! You are already registered for this event..." appears on the Registration page for an event if the user meets that case.

Similar code exists on the Event Info page, but doesn't work because it's trapped in an if{} statement. Instead what happens is a user doesn't see the button to register, but they don't receive a message telling them why. It's a small but annoying usability issue.

I have made improvements to the code and tested it. Now the message "Already registered" message appears on both the Registration page and the Event info page.