Fix users being able to answer the same question twice in the same server

Author: ABizzinotto

app/lib/discord/events/puzzle_answer.rb

@@ -26,9 +26,11 @@ def handle(event)
         )
         user.save if user.changed?
 
+        # Find server
+        server = Server.find_by(server_id: event.server.id)
 
         # Check if the user has already answered this puzzle
-        existing_answer = Answer.find_by(puzzle_id: puzzle.id, user_id: user.id, server_id: event.server.id)
+        existing_answer = Answer.find_by(puzzle_id: puzzle.id, user_id: user.id, server_id: server.id)
         if existing_answer
           # If the user has already answered, prevent them from changing their answer
           event.respond(